S&T Bancorp (STBA) 10-K 23 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 15, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Entity Registrant Name	S&T BANCORP INC
Entity Central Index Key	719,220
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		34,810,374
Entity Public Float			$ 991,599,929

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Cash and due from banks, including interest-bearing deposits of $41,639 and $57,048 at December 31, 2015 and 2014	$ 99,399	$ 109,580
Securities available-for-sale, at fair value	660,963	640,273
Loans held for sale	35,321	2,970
Portfolio loans, net of unearned income	5,027,612	3,868,746
Allowance for loan losses	(48,147)	(47,911)
Portfolio loans, net	4,979,465	3,820,835
Bank owned life insurance	70,175	62,252
Premises and equipment, net	49,127	38,166
Federal Home Loan Bank and other restricted stock, at cost	23,032	15,135
Goodwill	291,764	175,820
Other intangible assets, net	6,525	2,631
Other assets	102,583	97,024
Total Assets	6,318,354	4,964,686
LIABILITIES
Noninterest-bearing demand	1,227,766	1,083,919
Interest-bearing demand	616,188	335,099
Money market	605,184	376,612
Savings	1,061,265	1,027,095
Certificates of deposit	1,366,208	1,086,117
Total Deposits	4,876,611	3,908,842
Securities sold under repurchase agreements	62,086	30,605
Short-term borrowings	356,000	290,000
Long-term borrowings	117,043	19,442
Junior subordinated debt securities	45,619	45,619
Other liabilities	68,758	61,789
Total Liabilities	5,526,117	4,356,297
SHAREHOLDERS’ EQUITY
Common stock ($2.50 par value) Authorized—50,000,000 shares Issued—36,130,480 shares at December 31, 2015 and 31,197,365 shares at December 31, 2014 Outstanding—34,810,374 shares at December 31, 2015 and 29,796,397 shares at December 31, 2014	90,326	77,993
Additional paid-in capital	210,545	78,818
Retained earnings	544,228	504,060
Accumulated other comprehensive income (loss)	(16,457)	(13,833)
Treasury stock (1,320,106 shares at December 31, 2015 and 1,400,968 shares at December 31, 2014, at cost)	(36,405)	(38,649)
Total Shareholders’ Equity	792,237	608,389
Total Liabilities and Shareholders’ Equity	$ 6,318,354	$ 4,964,686

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Cash and due from banks, interest-bearing amounts	$ 41,639	$ 57,048
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	36,130,480	31,197,365
Common stock, shares outstanding (in shares)	34,810,374	29,796,397
Treasury stock, shares (in shares)	1,320,106	1,400,968

Consolidated Statements of Net

Consolidated Statements of Net Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
INTEREST INCOME
Loans, including fees	$ 188,012	$ 147,293	$ 142,492
Investment Securities:
Taxable	9,792	8,983	7,478
Tax-exempt	3,954	3,857	3,401
Dividends	1,790	390	385
Total Interest Income	203,548	160,523	153,756
INTEREST EXPENSE
Deposits	12,944	10,128	11,406
Borrowings and junior subordinated debt securities	3,053	2,353	3,157
Total Interest Expense	15,997	12,481	14,563
NET INTEREST INCOME	187,551	148,042	139,193
Provision for loan losses	10,388	1,715	8,311
Net Interest Income After Provision for Loan Losses	177,163	146,327	130,882
NONINTEREST INCOME
Securities (losses) gains, net	(34)	41	5
Debit and credit card fees	12,113	10,781	10,931
Service charges on deposit accounts	11,642	10,559	10,488
Wealth management fees	11,444	11,343	10,696
Insurance fees	5,500	5,955	6,248
Gain on sale of merchant card servicing business	0	0	3,093
Mortgage banking	2,554	917	2,123
Other	7,814	6,742	7,943
Total Noninterest Income	51,033	46,338	51,527
NONINTEREST EXPENSE
Salaries and employee benefits	68,252	60,442	60,847
Net occupancy	10,652	8,211	8,018
Data processing	9,677	8,737	8,263
Furniture and equipment	6,093	5,317	4,883
Marketing	4,224	3,316	2,929
Other taxes	3,616	2,905	3,743
FDIC insurance	3,416	2,436	2,772
Professional services and legal	3,365	3,717	4,184
Merger related expenses	3,167	689	838
Other	24,255	21,470	20,915
Total Noninterest Expense	136,717	117,240	117,392
Income Before Taxes	91,479	75,425	65,017
Provision for income taxes	24,398	17,515	14,478
Net Income Available to Common Shareholders	$ 67,081	$ 57,910	$ 50,539
Earnings per common share—basic (in USD per share)	$ 1.98	$ 1.95	$ 1.70
Earnings per common share—diluted (in USD per share)	1.98	1.95	1.70
Dividends declared per common share (in USD per share)	$ 0.73	$ 0.68	$ 0.61

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net Income	$ 67,081	$ 57,910	$ 50,539
Other Comprehensive Income (Loss), Before Tax:
Net change in unrealized (losses) gains on securities available-for-sale	(663)	11,825	(16,928)
Net available-for-sale securities losses (gains) reclassified into earnings	34	(41)	(5)
Adjustment to funded status of employee benefit plans	(3,551)	(13,394)	18,299
Other Comprehensive Income (Loss), Before Tax	(4,180)	(1,610)	1,366
Income tax benefit (expense) related to items of other comprehensive income	1,556	471	(478)
Other Comprehensive Income (Loss), After Tax	(2,624)	(1,139)	888
Comprehensive Income	$ 64,457	$ 56,771	$ 51,427

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2012	$ 537,422	$ 77,993	$ 77,458	$ 436,039	$ (13,582)	$ (40,486)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	50,539			50,539
Other comprehensive income (loss), net of tax	888				888
Cash dividends declared	(18,137)			(18,137)
Treasury stock issued	(88)			(283)		195
Recognition of restricted stock compensation expense	586		586
Tax expense from stock-based compensation	96		96
Ending balance at Dec. 31, 2013	571,306	77,993	78,140	468,158	(12,694)	(40,291)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	57,910			57,910
Other comprehensive income (loss), net of tax	(1,139)				(1,139)
Cash dividends declared	(20,203)			(20,203)
Treasury stock issued	(163)			(1,805)		1,642
Recognition of restricted stock compensation expense	933		933
Tax expense from stock-based compensation	16		16
Issuance costs	(271)		(271)
Ending balance at Dec. 31, 2014	608,389	77,993	78,818	504,060	(13,833)	(38,649)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	67,081			67,081
Other comprehensive income (loss), net of tax	(2,624)				(2,624)
Cash dividends declared	(24,487)			(24,487)
Common stock issued in acquisition	142,469	12,333	130,136
Treasury stock issued	(182)			(2,426)		2,244
Recognition of restricted stock compensation expense	1,670		1,670
Tax expense from stock-based compensation	53		53
Issuance costs	(132)		(132)
Ending balance at Dec. 31, 2015	$ 792,237	$ 90,326	$ 210,545	$ 544,228	$ (16,457)	$ (36,405)

Consolidated Statements of Cha7

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash dividends declared, per share (in USD per share)	$ 0.73	$ 0.68	$ 0.61
Treasury stock, shares net	80,862	58,762	5,516
Common Stock
Common stock issued in acquisition, shares	4,933,115

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES
Net Income	$ 67,081	$ 57,910	$ 50,539
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	10,388	1,715	8,311
Provision for unfunded loan commitments	258	(655)	(60)
Net depreciation, amortization and accretion	356	4,703	5,333
Net amortization of discounts and premiums on securities	3,600	3,680	3,826
Stock-based compensation expense	1,636	975	687
Securities losses, (gains), net	34	(41)	(5)
Net gain on sale of merchant card servicing business	0	0	(3,093)
Tax benefit from stock-based compensation	(53)	(16)	(96)
Mortgage loans originated for sale	(107,489)	(42,842)	(66,695)
Proceeds from the sale of loans	99,458	42,361	87,932
Deferred income taxes	(427)	1,536	(2,358)
Gain on sale of fixed assets	(179)	(33)	0
Gain on the sale of loans, net	(1,044)	(353)	(874)
Net increase in interest receivable	(2,744)	(933)	(130)
Net decrease in interest payable	(193)	(127)	(2,005)
Net (increase) decrease in other assets	(11,396)	7,628	25,681
Net increase (decrease) in other liabilities	1,298	2,595	(20,917)
Net Cash Provided by Operating Activities	60,584	78,103	86,076
INVESTING ACTIVITIES
Proceeds from maturities, prepayments and calls of securities available-for-sale	50,142	57,092	66,744
Proceeds from sales of securities available-for-sale	11,119	1,418	94
Purchases of securities available-for-sale	(74,712)	(181,213)	(144,752)
Net purchases of Federal Home Loan Bank stock	(855)	(1,506)	1,685
Net increase in loans	(383,575)	(313,264)	(241,172)
Proceeds from the sale of loans not originated for resale	2,880	5,408	5,158
Purchases of premises and equipment	(5,133)	(5,079)	(2,833)
Proceeds from the sale of premises and equipment	467	96	643
Net cash paid in excess of cash acquired from bank merger	(16,347)	0	0
Proceeds from the sale of merchant card servicing business	0	0	4,750
Proceeds from surrender of bank owned life insurance	10,277	0	0
Net Cash Used in Investing Activities	(405,737)	(437,048)	(309,683)
FINANCING ACTIVITIES
Net increase (decrease) in core deposits	195,589	240,948	(22,767)
Net increase (decrease) in certificates of deposit	51,209	(4,549)	56,174
Net (decrease) increase in short-term borrowings	(2,660)	150,000	65,000
Net increase (decrease) in securities sold under repurchase agreements	31,481	(3,242)	(28,735)
Proceeds from long-term borrowings	100,000	0	0
Repayments of long-term borrowings	(2,399)	(2,367)	(12,291)
Repayment of junior subordinated debt	(13,500)	0	(45,000)
Treasury shares issued-net	(182)	(163)	(88)
Common stock Issuance costs	(132)	(271)	0
Cash dividends paid to common shareholders	(24,487)	(20,203)	(18,137)
Tax benefit from stock-based compensation	53	16	96
Net Cash Provided by (Used in) Financing Activities	334,972	360,169	(5,748)
Net (decrease) increase in cash and cash equivalents	(10,181)	1,224	(229,355)
Cash and cash equivalents at beginning of year	109,580	108,356	337,711
Cash and Cash Equivalents at End of Year	99,399	109,580	108,356
Supplemental Disclosures
Transfers to other real estate owned and other repossessed assets	843	586	1,238
Interest paid	15,878	12,609	16,568
Income taxes paid, net of refunds	23,175	18,075	13,130
Loans transferred to held for sale	23,277	0	5,158
Net assets (liabilities) from acquisitions, excluding cash and cash equivalents	$ 43,433	$ 0	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations S&T Bancorp, Inc., or S&T, was incorporated on March 17, 1983 under the laws of the Commonwealth of Pennsylvania as a bank holding company and has three wholly owned subsidiaries, S&T Bank, 9th Street Holdings, Inc. and STBA Capital Trust I. We own a 50 percent interest in Commonwealth Trust Credit Life Insurance Company, or CTCLIC. We are presently engaged in nonbanking activities through the following five entities: 9th Street Holdings, Inc.; S&T Bancholdings, Inc.; CTCLIC; S&T Insurance Group, LLC and Stewart Capital Advisors, LLC. 9th Street Holdings, Inc. and S&T Bancholdings, Inc. are investment holding companies. CTCLIC, which is a joint venture with another financial institution, acts as a reinsurer of credit life, accident and health insurance policies sold by S&T Bank and the other institution. S&T Insurance Group, LLC, through its subsidiaries, offers a variety of insurance products. Stewart Capital Advisors, LLC is a registered investment advisor that manages private investment accounts for individuals and institutions and advises the Stewart Capital Mid Cap Fund. On October 29, 2014, S&T and Integrity Bancshares, Inc., or Integrity, based in Camp Hill, Pennsylvania, entered into an agreement to acquire Integrity Bancshares, Inc. and the transaction was completed on March 4, 2015. Integrity Bank was subsequently merged into S&T Bank on May 8, 2015. S&T Bank is operating under the name "Integrity Bank - A Division of S&T Bank" in south-central Pennsylvania. Accounting Policies Our financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP. In preparing the financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the dates of the balance sheets and revenues and expenses for the periods then ended. Actual results could differ from those estimates. Our significant accounting policies are described below. Principles of Consolidation The Consolidated Financial Statements include the accounts of S&T and its wholly owned subsidiaries. All significant intercompany transactions have been eliminated in consolidation. Investments of 20 percent to 50 percent of the outstanding common stock of investees are accounted for using the equity method of accounting. Reclassification Certain amounts in prior years’ financial statements and footnotes have been reclassified to conform to the current year’s presentation. The reclassifications had no significant effect on our results of operations or financial condition. Business Combinations We account for business combinations using the acquisition method of accounting. Under this method of accounting, the acquired company’s net assets are recorded at fair value at the date of acquisition, and the results of operations of the acquired company are combined with our results from that date forward. Acquisition costs are expensed when incurred. The difference between the purchase price and the fair value of the net assets acquired (including identified intangibles) is recorded as goodwill. Fair Value Measurements We use fair value measurements when recording and disclosing certain financial assets and liabilities. Securities available-for-sale, trading assets and derivative financial instruments are recorded at fair value on a recurring basis. Additionally, from time to time, we may be required to record other assets at fair value on a nonrecurring basis, such as loans held for sale, impaired loans, other real estate owned, or OREO, and other repossessed assets, mortgage servicing rights, or MSRs, and certain other assets. Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants at the measurement date. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets or liabilities; it is not a forced transaction. In determining fair value, we use various valuation approaches, including market, income and cost approaches. The fair value standard establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing an asset or liability, which are developed, based on market data we have obtained from independent sources. Unobservable inputs reflect our estimates of assumptions that market participants would use in pricing an asset or liability, which are developed based on the best information available in the circumstances. The fair value hierarchy gives the highest priority to unadjusted quoted market prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). The fair value hierarchy is broken down into three levels based on the reliability of inputs as follows: Level 1: valuation is based upon unadjusted quoted market prices for identical instruments traded in active markets. Level 2: valuation is based upon quoted market prices for similar instruments traded in active markets, quoted market prices for identical or similar instruments traded in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by market data. Level 3: valuation is derived from other valuation methodologies, including discounted cash flow models and similar techniques that use significant assumptions not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in determining fair value. A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Our policy is to recognize transfers between any of the fair value hierarchy levels at the end of the reporting period in which the transfer occurred. The following are descriptions of the valuation methodologies that we use for financial instruments recorded at fair value on either a recurring or nonrecurring basis. Recurring Basis Securities Available-for-Sale Securities available-for-sale include both debt and equity securities. We obtain fair values for debt securities from a third-party pricing service which utilizes several sources for valuing fixed-income securities. We validate prices received from our pricing service through comparison to a secondary pricing service and broker quotes. We review the methodologies of the pricing service which provides us with a sufficient understanding of the valuation models, assumptions, inputs and pricing to reasonably measure the fair value of our debt securities. The market evaluation sources for debt securities include observable inputs rather than significant unobservable inputs and are classified as Level 2. The service provider utilizes pricing models that vary by asset class and include available trade, bid and other market information. Generally, the methodologies include broker quotes, proprietary models, and vast descriptive terms and conditions databases, as well as extensive quality control programs. Marketable equity securities that have an active, quotable market are classified as Level 1. Marketable equity securities that are quotable, but are thinly traded or inactive, are classified as Level 2. Marketable equity securities that are not readily traded and do not have a quotable market are classified as Level 3. Trading Assets We use quoted market prices to determine the fair value of our trading assets. Our trading assets are held in a Rabbi Trust under a deferred compensation plan and are invested in readily quoted mutual funds. Accordingly, these assets are classified as Level 1. Derivative Financial Instruments We use derivative instruments, including interest rate swaps for commercial loans with our customers, interest rate lock commitments and the sale of mortgage loans in the secondary market. We calculate the fair value for derivatives using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. Each valuation considers the contractual terms of the derivative, including the period to maturity, and uses observable market based inputs, such as interest rate curves and implied volatilities. Accordingly, derivatives are classified as Level 2. We incorporate credit valuation adjustments into the valuation models to appropriately reflect both our own nonperformance risk and the respective counterparties’ nonperformance risk in calculating fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting and any applicable credit enhancements and collateral postings. Nonrecurring Basis Loans Held for Sale Loans held for sale consist of 1-4 family residential loans originated for sale in the secondary market and, from time to time, certain loans transferred from the loan portfolio to loans held for sale, all of which are carried at the lower of cost or fair value. The fair value of 1-4 family residential loans is based on the principal or most advantageous market currently offered for similar loans using observable market data. The fair value of the loans transferred from the loan portfolio is based on the amounts offered for these loans in currently pending sales transactions. Loans held for sale carried at fair value are classified as Level 3. Impaired Loans Impaired loans are carried at the lower of carrying value or fair value. Fair value is determined as the recorded investment balance less any specific reserve. We establish specific reserves based on the following three impairment methods: 1) the present value of expected future cash flows discounted at the loan’s original effective interest rate, 2) the loan’s observable market price or 3) the fair value of the collateral less estimated selling costs when the loan is collateral dependent and we expect to liquidate the collateral. However, if repayment is expected to come from the operation of the collateral, rather than liquidation, then we do not consider estimated selling costs in determining the fair value of the collateral. Collateral values are generally based upon appraisals by approved, independent state certified appraisers. Appraisals may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or our knowledge of the borrower and the borrower’s business. Impaired loans carried at fair value are classified as Level 3. OREO and Other Repossessed Assets OREO and other repossessed assets obtained in partial or total satisfaction of a loan are recorded at the lower of recorded investment in the loan or fair value less cost to sell. Subsequent to foreclosure, these assets are carried at the lower of the amount recorded at acquisition date or fair value less cost to sell. Accordingly, it may be necessary to record nonrecurring fair value adjustments. Fair value, when recorded, is generally based upon appraisals by approved, independent state certified appraisers. Like impaired loans, appraisals on OREO may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or other information available to us. OREO and other repossessed assets carried at fair value are classified as Level 3. Mortgage Servicing Rights The fair value of MSRs is determined by calculating the present value of estimated future net servicing cash flows, considering expected mortgage loan prepayment rates, discount rates, servicing costs and other economic factors, which are determined based on current market conditions. The expected rate of mortgage loan prepayments is the most significant factor driving the value of MSRs. MSRs are considered impaired if the carrying value exceeds fair value. The valuation model includes significant unobservable inputs; therefore, MSRs are classified as Level 3. Other Assets We measure certain other assets at fair value on a nonrecurring basis. Fair value is based on the application of lower of cost or fair value accounting, or write-downs of individual assets. Valuation methodologies used to measure fair value are consistent with overall principles of fair value accounting and consistent with those described above. Financial Instruments In addition to financial instruments recorded at fair value in our financial statements, fair value accounting guidance requires disclosure of the fair value of all of an entity’s assets and liabilities that are considered financial instruments. The majority of our assets and liabilities are considered financial instruments. Many of these instruments lack an available trading market as characterized by a willing buyer and willing seller engaged in an exchange transaction. Also, it is our general practice and intent to hold our financial instruments to maturity and to not engage in trading or sales activities with respect to such financial instruments. For fair value disclosure purposes, we substantially utilize the fair value measurement criteria as required and explained above. In cases where quoted fair values are not available, we use present value methods to determine the fair value of our financial instruments. Cash and Cash Equivalents The carrying amounts reported in the Consolidated Balance Sheets for cash and due from banks, including interest-bearing deposits, approximate fair value. Loans The fair value of variable rate performing loans that may reprice frequently at short-term market rates is based on carrying values adjusted for credit risk. The fair value of variable rate performing loans that reprice at intervals of one year or longer, such as adjustable rate mortgage products, is estimated using discounted cash flow analyses that utilize interest rates currently being offered for similar loans and adjusted for credit risk. The fair value of fixed rate performing loans is estimated using a discounted cash flow analysis that utilizes interest rates currently being offered for similar loans and adjusted for credit risk. The fair value of impaired nonperforming loans is based on their carrying values less any specific reserve. The carrying amount of accrued interest approximates fair value. Bank Owned Life Insurance Fair value approximates net cash surrender value of bank owned life insurance, or BOLI. Federal Home Loan Bank, or FHLB, and Other Restricted Stock It is not practical to determine the fair value of our FHLB and other restricted stock due to the restrictions placed on the transferability of these stocks; it is presented at carrying value. Deposits The fair values disclosed for deposits without defined maturities (e.g., noninterest and interest-bearing demand, money market and savings accounts) are by definition equal to the amounts payable on demand. The carrying amounts for variable rate, fixed-term time deposits approximate their fair values. Estimated fair values for fixed rate and other time deposits are based on discounted cash flow analysis using interest rates currently offered for time deposits with similar terms. The carrying amount of accrued interest approximates fair value. Short-Term Borrowings The carrying amounts of securities sold under repurchase agreements, or REPOs, and other short-term borrowings approximate their fair values. Long-Term Borrowings The fair values disclosed for fixed rate long-term borrowings are determined by discounting their contractual cash flows using current interest rates for long-term borrowings of similar remaining maturities. The carrying amounts of variable rate long-term borrowings approximate their fair values. Junior Subordinated Debt Securities The variable rate junior subordinated debt securities reprice quarterly; therefore, the carrying values approximate their fair values. Loan Commitments and Standby Letters of Credit Off-balance sheet financial instruments consist of commitments to extend credit and letters of credit. Except for interest rate lock commitments, estimates of the fair value of these off-balance sheet items are not made because of the short-term nature of these arrangements and the credit standing of the counterparties. Other Estimates of fair value are not made for items that are not defined as financial instruments, including such items as our core deposit intangibles and the value of our trust operations. Cash and Cash Equivalents We consider cash and due from banks, interest-bearing deposits with banks and federal funds sold as cash and cash equivalents. Securities We determine the appropriate classification of securities at the time of purchase. All securities, including both debt and equity securities, are classified as available-for-sale. These are securities that we intend to hold for an indefinite period of time, but that may be sold in response to changes in interest rates, prepayment risk, liquidity needs or other factors. Such securities are carried at fair value with net unrealized gains and losses deemed to be temporary, reported as a component of other comprehensive income (loss), net of tax. Realized gains and losses on the sale of available-for-sale securities and other-than-temporary impairment, or OTTI, charges are recorded within noninterest income in the Consolidated Statements of Net Income. Realized gains and losses on the sale of securities are determined using the specific-identification method. Bond premiums are amortized to the call date and bond discounts are accreted to the maturity date, both on a level yield basis. An investment security is considered impaired if its fair value is less than its cost or amortized cost basis. We perform a quarterly review of our securities to identify those that may indicate an OTTI. Our policy for OTTI within the marketable equity securities portfolio generally requires an impairment charge when the security is in a loss position for 12 consecutive months, unless facts and circumstances would suggest the need for an OTTI prior to that time. Our policy for OTTI within the debt securities portfolio is based upon a number of factors, including but not limited to, the length of time and extent to which the estimated fair value has been less than cost, the financial condition of the underlying issuer, the ability of the issuer to meet contractual obligations, the best estimate of the impairment charge representing credit losses, the likelihood of the security’s ability to recover any decline in its estimated fair value and whether management intends to sell the security or if it is more likely than not that management will be required to sell the investment security prior to the security’s recovery of any decline in its estimated fair value. If the impairment is considered other-than-temporary based on management’s review, the impairment must be separated into credit and non-credit components. The credit component is recognized in the Consolidated Statements of Net Income and the non-credit component is recognized in other comprehensive income (loss), net of applicable taxes. Loans Held for Sale Loans held for sale consist of 1-4 family residential loans originated for sale in the secondary market and from time to time, certain loans transferred from the loan portfolio to loans held for sale, all of which are carried at the lower of cost or fair value. If a loan is transferred from the loan portfolio to the held for sale category, any write-down in the carrying amount of the loan at the date of transfer is recorded as a charge-off against the allowance for loan losses, or ALL. Subsequent declines in fair value are recognized as a charge to noninterest income. When a loan is placed in the held for sale category, we stop amortizing the related deferred fees and costs. The remaining unamortized fees and costs are recognized as part of the cost basis of the loan at the time it is sold. Gains and losses on sales of loans held for sale are included in other noninterest income in the Consolidated Statements of Net Income. Loans Loans are reported at the principal amount outstanding net of unearned income, unamortized premiums or discounts and deferred origination fees and costs. We defer certain nonrefundable loan origination and commitment fees. Accretion of discounts and amortization of premiums on loans are included in interest income in the Consolidated Statements of Net Income. Loan origination fees and direct loan origination costs are deferred and amortized as an adjustment of loan yield over the respective lives of the loans without consideration of anticipated prepayments. If a loan is paid off, the remaining unaccreted or unamortized net origination fees and costs are immediately recognized into income or expense. Interest is accrued and interest income is recognized on loans as earned. Acquired loans are recorded at fair value on the date of acquisition with no carryover of the related ALL. Determining the fair value of the acquired loans involves estimating the principal and interest cash flows expected to be collected on the loans and discounting those cash flows at a market rate of interest. In estimating the fair value of our acquired loans, we consider a number of factors including the loan term, internal risk rating, delinquency status, prepayment rates, recovery periods, estimated value of the underlying collateral and the current interest rate environment. Closed-end installment loans, amortizing loans secured by real estate and any other loans with payments scheduled monthly are reported past due when the borrower is in arrears two or more monthly payments. Other multi-payment obligations with payments scheduled other than monthly are reported past due when one scheduled payment is due and unpaid for 30 days or more. Generally, consumer loans are charged off against the ALL upon the loan reaching 90 days past due. Commercial loans are charged off as management becomes aware of facts and circumstances that raise doubt as to the collectability of all or a portion of the principal and when we believe a confirmed loss exists. Nonaccrual or Nonperforming Loans We stop accruing interest on a loan when the borrower’s payment is 90 days past due. Loans are also placed on nonaccrual status when payment is not past due, but we have doubt about the borrower’s ability to comply with contractual repayment terms. When the interest accrual is discontinued, all unpaid accrued interest is reversed against interest income. Interest income is recognized on nonaccrual loans on a cash basis if recovery of the remaining principal is reasonably assured. As a general rule, a nonaccrual loan may be restored to accrual status when its principal and interest is paid current and the bank expects repayment of the remaining contractual principal and interest, or when the loan otherwise becomes well secured and in the process of collection. Troubled Debt Restructurings Troubled debt restructurings, or TDRs, are loans where we, for economic or legal reasons related to a borrower’s financial difficulty, grant a concession to the borrower that we would not otherwise grant. We strive to identify borrowers in financial difficulty early and work with them to modify the terms before their loan reaches nonaccrual status. These modified terms generally include extensions of maturity dates at a stated interest rate lower than the current market rate for a new loan with similar risk characteristics, reductions in contractual interest rates or principal deferment. While unusual, there may be instances of principal forgiveness. These modifications are generally for longer term periods that would not be considered insignificant. Additionally, we classify loans where the debt obligation has been discharged through a Chapter 7 Bankruptcy and not reaffirmed as TDRs. We individually evaluate all substandard commercial loans that experienced a forbearance or change in terms agreement, as well as all substandard consumer and residential mortgage loans that entered into an agreement to modify their existing loan to determine if they should be designated as TDRs. All TDRs will be reported as impaired loans for the remaining life of the loan, unless the restructuring agreement specifies an interest rate equal to or greater than the rate that would be accepted at the time of the restructuring for a new loan with comparable risk and it is fully expected that the remaining principal and interest will be collected according to the restructured agreement. Further, all impaired loans are reported as nonaccrual loans unless the loan is a TDR that has met the requirements to be returned to accruing status. TDRs can be returned to accruing status if the ultimate collectability of all contractual amounts due, according to the restructured agreement, is not in doubt and there is a period of a minimum of six months of satisfactory payment performance by the borrower either immediately before or after the restructuring. Allowance for Loan Losses The ALL reflects our estimates of probable losses inherent in the loan portfolio at the balance sheet date. The methodology for determining the ALL has two main components: evaluation and impairment tests of individual loans and evaluation and impairment tests of certain groups of homogeneous loans with similar risk characteristics. A loan is considered impaired when it is probable that we will be unable to collect all principal and interest payments due according to the original contractual terms of the loan agreement. We individually evaluate all substandard and nonaccrual commercial loans greater than $0.5 million for impairment. TDRs will be reported as an impaired loan for the remaining life of the loan, unless the restructuring agreement specifies an interest rate equal to or greater than the rate that would be accepted at the time of the restructuring for a new loan with comparable risk and it is fully expected that the remaining principal and interest will be collected according to the restructured agreement. For all TDRs, regardless of size, as well as all other impaired loans, we conduct further analysis to determine the probable loss and assign a specific reserve to the loan if deemed appropriate. Specific reserves are established based upon the following three impairment methods: 1) the present value of expected future cash flows discounted at the loan’s original effective interest rate, 2) the loan’s observable market price or 3) the estimated fair value of the collateral if the loan is collateral dependent. Our impairment evaluations consist primarily of the fair value of collateral method because most of our loans are collateral dependent. Collateral values are discounted to consider disposition costs when appropriate. A specific reserve is established or a charge-off is taken if the fair value of the impaired loan is less than the recorded investment in the loan balance. The ALL for homogeneous loans is calculated using a systematic methodology with both a quantitative and a qualitative analysis that is applied on a quarterly basis. The ALL model is comprised of five distinct portfolio segments: 1) Commercial Real Estate, or CRE, 2) Commercial and Industrial, or C&I, 3) Commercial Construction, 4) Consumer Real Estate and 5) Other Consumer. Each segment has a distinct set of risk characteristics monitored by management. We further assess and monitor risk and performance at a more disaggregated level which includes our internal risk rating system for the commercial segments and type of collateral, lien position and loan-to-value, or LTV, for the consumer segments. We first apply historical loss rates to pools of loans with similar risk characteristics. Loss rates are calculated by historical charge-offs that have occurred within each pool of loans over the loss emergence period, or LEP. The LEP is an estimate of the average amount of time from when an event happens that causes the borrower to be unable to pay on a loan until the loss is confirmed through a loan charge-off. In conjunction with our annual review of the ALL assumptions, we have updated our analysis of LEPs for our Commercial and Consumer loan portfolio segments using our loan charge-off history. The analysis showed that the LEP for our C&I, has shortened and our CRE, and Commercial Construction portfolio segments have not changed. We estimate the LEP to be 2 years for C&I, compared to 2.5 years in the prior year, and 3.5 years for both CRE and Commercial Construction. Our analysis showed an LEP for Consumer Real Estate of 3.5 years and Other Consumer of 1.25 years. This compares to 2 years for both Consumer Real Estate and Other Consumer in the prior year when peer data was being utilized to estimate the LEP. We believe that our actual experience captured through our internal analysis better reflects the inherent risk in these portfolios compared to the peer data used in prior years. Another key assumption is the look-back period, or LBP, which represents the historical data period utilized to calculate loss rates. We lengthened the LBP for all Commercial and Consumer portfolio segments in order to capture relevant historical data believed to be reflective of losses inherent in the portfolios. We use 6.5 years for our LBP for all portfolio segments which encompasses our loss experience during the Great Recession and our more recent improved loss experience. After consideration of the historic loss calculations, management applies additional qualitative adjustments so that the ALL is reflective of the inherent losses that exist in the loan portfolio at the balance sheet date. The following qualitative factors are considered in the ALL: 1) Changes in our lending policies and procedures, including underwriting standards, collection, charge-off and recovery practices not considered elsewhere in estimating credit losses; 2) Changes in national, regional, and local economic and business conditions and developments that affect the collectability of the portfolio, including the condition of various market segments; 3) Changes in the nature and volume of our loan portfolio and terms of loans; 4) Changes in the experience, ability and depth of our lending management and staff; 5) Changes in the volume and severity of past due loans, the volume of nonaccrual loans, and the volume and severity of adversely classified or graded loans; 6) Changes in the quality of our loan review system; 7) Changes in the value of the underlying collateral for collateral-dependent loans; 8) The existence and effect of any concentrations of credit and changes in the level of such concentrations; and 9) The effect of external factors such as competition and legal and regulatory requirements on the level of estimated credit losses in our current loan portfolio. The changes made to the ALL assumptions were applied prospectively and did not result in a material change to the total ALL. Lengthening the LBP does increase the historical loss rates and therefore the quantitative component of the ALL. We believe this makes the quantitative component of the ALL more reflective of inherent losses that exist within the loan portfolio, which resulted in a decrease in the qualitative component of the ALL. Loans acquired with evidence of credit deterioration were evaluated and not considered to be significant. The premium or discount estimated through the loan fair value calculation is recognized into interest income on a level yield or straight-line basis over the remaining contractual life of the loans. Additional credit deterioration on acquired loans, in excess of the original credit discount embedded in the fair value determination on the date of acquisition, will be recognized in the ALL through the provision for loan losses. Our ALL Committee meets quarterly to verify the overall adequacy of the ALL. Additionally, on an annual basis, the ALL Committee meets to validate our ALL methodology. This validation includes reviewing the loan segmentation, LEP, LBP and the qualitative framework. As a result of this ongoing monitoring process, we may make changes to our ALL to be responsive to the economi

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Business Combinations	BUSINESS COMBINATIONS On March 4, 2015, we completed the acquisition of 100 percent of the voting shares of Integrity Bancshares, Inc., or Integrity, located in Camp Hill, Pennsylvania, in a tax-free reorganization transaction structured as a merger of Integrity with and into S&T, with S&T being the surviving entity. As a result of the Integrity merger, or the Merger, Integrity Bank, the wholly owned subsidiary bank of Integrity, became a separate wholly owned subsidiary bank of S&T. The merger of Integrity Bank into S&T Bank, with S&T Bank surviving the merger, and related system conversion occurred on May 8, 2015. Integrity shareholders were entitled to elect to receive for each share of Integrity common stock either $52.50 in cash or 2.0627 shares of S&T common stock subject to allocation and proration procedures in the merger agreement. The total purchase price was approximately $172.0 million which included $29.5 million of cash and 4,933,115 S&T common shares at a fair value of $28.88 per share. The fair value of $28.88 per share of S&T common stock was based on the March 4, 2015 closing price. The Merger was accounted for under the acquisition method of accounting and our consolidated financial statements include all Integrity Bank transactions from March 4, 2015, until it was merged into S&T Bank on May 8, 2015. The assets acquired and liabilities assumed were recorded at their respective fair values and represent management’s estimates based on available information. Purchase accounting guidance allows for a reasonable period of time following an acquisition for the acquirer to obtain the information necessary to complete the accounting for a business combination. This period is known as the measurement period and shall not exceed one year from the acquisition date. As of December 31, 2015, an additional $1.1 million of purchase accounting adjustments were recognized that increased goodwill. The measurement period adjustments primarily related to a $0.8 million reduction in the fair value of land and $0.3 million to deferred taxes. Goodwill of $115.9 million was calculated as the excess of the consideration exchanged over the fair value of the identifiable net assets acquired. The goodwill arising from the Merger consists largely of the synergies and economies of scale expected from combining the operations of S&T and Integrity. All of the goodwill was assigned to our Community Banking segment. The goodwill recognized will not be deductible for tax purposes. The following table summarizes total consideration, assets acquired and liabilities assumed as of December 31, 2015: (dollars in thousands) Consideration Paid Cash $ 29,510 Common stock 142,469 Fair Value of Total Consideration $ 171,979 Fair Value of Assets Acquired Cash and cash equivalents $ 13,163 Securities and other investments 11,502 Loans 788,687 Bank owned life insurance 15,974 Premises and equipment 10,855 Core deposit intangible 5,713 Other assets 18,994 Total Assets Acquired 864,888 Fair Value of Liabilities Assumed Deposits 722,308 Borrowings 82,286 Other liabilities 4,259 Total Liabilities Assumed 808,853 Total Fair Value of Identifiable Net Assets 56,035 Goodwill $ 115,944 Loans acquired in the Merger were recorded at fair value with no carryover of the related ALL. Determining the fair value of the loans involves estimating the amount and timing of principal and interest cash flows expected to be collected on the loans and discounting those cash flows at a market rate of interest. The fair value of the loans acquired was $788.7 million net of a $14.8 million discount. The discount may be accreted to interest income over the remaining contractual life of the loans. Acquired loans included $331.6 million of CRE, $184.2 million of C&I, $92.4 million of commercial construction, $116.9 million of residential mortgage, $25.6 million of home equity, $36.1 million of installment and other consumer and $1.9 million of consumer construction. Direct costs related to the Merger were expensed as incurred. During 2015, we recognized $3.2 million of merger related expenses, including $1.3 million for data processing contract termination and system conversion costs, $1.2 million in legal and professional expenses, $0.4 million in severance payments and $0.3 million in other expenses. The following table presents unaudited pro forma financial information which combines the historical consolidated statements of income of S&T and Integrity to give effect to the Merger as if it had occurred on January 1, 2014, for the periods presented. Unaudited Pro Forma Information (dollars in thousands, except per share data) 2015 2014 Total revenue (1) $ 240,581 $ 232,635 Net income (2) $ 68,850 $ 70,001 Earnings per common share: (2) Basic $ 1.78 $ 2.02 Diluted $ 1.77 $ 2.02 (1) Total pro forma revenue is defined as net interest income plus non-interest income, excluding gains and losses on sales of investment securities available-for-sale. ( 2) Excludes merger expenses Pro forma adjustments include intangible amortization expense, net amortization or accretion of valuation amounts and income tax expense. The pro forma results are not indicative of the results of operations that would have occurred had the Merger taken place at the beginning of the periods presented nor are they intended to be indicative of results that may occur in the future.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE The following table reconciles the numerators and denominators of basic and diluted EPS: Years ended December 31, (dollars in thousands, except share and per share data) 2015 2014 2013 Numerator for Earnings per Common Share—Basic: Net income $ 67,081 $ 57,910 $ 50,539 Less: Income allocated to participating shares 280 165 147 Net Income Allocated to Common Shareholders $ 66,801 $ 57,745 $ 50,392 Numerator for Earnings per Common Share—Diluted: Net income $ 67,081 $ 57,910 $ 50,539 Denominators: Weighted Average Common Shares Outstanding—Basic 33,812,990 29,683,103 29,647,231 Add: Dilutive potential common shares 35,092 25,621 35,322 Denominator for Treasury Stock Method—Diluted 33,848,082 29,708,724 29,682,553 Weighted Average Common Shares Outstanding—Basic 33,812,990 29,683,103 29,647,231 Add: Average participating shares outstanding 141,558 84,918 86,490 Denominator for Two-Class Method—Diluted 33,954,548 29,768,021 29,733,721 Earnings per common share—basic $ 1.98 $ 1.95 $ 1.70 Earnings per common share—diluted $ 1.98 $ 1.95 $ 1.70 Warrants considered anti-dilutive excluded from dilutive potential common shares - exercise price $31.53 per share, expires January 2019 517,012 517,012 517,012 Stock options considered anti-dilutive excluded from dilutive potential common shares — 419,538 619,418 Restricted stock considered anti-dilutive excluded from dilutive potential common shares 106,466 59,297 51,169

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The following tables present our assets and liabilities that are measured at fair value on a recurring basis by fair value hierarchy level at December 31, 2015 and 2014. There were no transfers between Level 1 and Level 2 for items measured at fair value on a recurring basis during the periods presented. December 31, 2015 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Securities available-for-sale: U.S. Treasury securities $ — $ 14,941 $ — $ 14,941 Obligations of U.S. government corporations and agencies — 263,303 — 263,303 Collateralized mortgage obligations of U.S. government corporations and agencies — 128,835 — 128,835 Residential mortgage-backed securities of U.S. government corporations and agencies — 40,125 — 40,125 Commercial mortgage-backed securities of U.S. government corporations and agencies — 69,204 — 69,204 Obligations of states and political subdivisions — 134,886 — 134,886 Marketable equity securities — 9,669 — 9,669 Total securities available-for-sale — 660,963 — 660,963 Trading securities held in a Rabbi Trust 4,021 — — 4,021 Total securities 4,021 660,963 — 664,984 Derivative financial assets: Interest rate swaps — 11,295 — 11,295 Interest rate lock commitments — 261 — 261 Total Assets $ 4,021 $ 672,519 $ — $ 676,540 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 11,276 $ — $ 11,276 Forward sale contracts — 5 — 5 Total Liabilities $ — $ 11,281 $ — $ 11,281 December 31, 2014 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Securities available-for-sale: U.S. Treasury securities $ — $ 14,880 $ — $ 14,880 Obligations of U.S. government corporations and agencies — 269,285 — 269,285 Collateralized mortgage obligations of U.S. government corporations and agencies — 118,006 — 118,006 Residential mortgage-backed securities of U.S. government corporations and agencies — 46,668 — 46,668 Commercial mortgage-backed securities of U.S. government corporations and agencies — 39,673 — 39,673 Obligations of states and political subdivisions — 142,702 — 142,702 Marketable equity securities 178 8,881 — 9,059 Total securities available-for-sale 178 640,095 — 640,273 Trading securities held in a Rabbi Trust 3,456 — — 3,456 Total securities 3,634 640,095 — 643,729 Derivative financial assets: Interest rate swaps — 12,981 — 12,981 Interest rate lock commitments — 235 — 235 Total Assets $ 3,634 $ 653,311 $ — $ 656,945 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 12,953 $ — $ 12,953 Forward Sale Contracts — 57 57 Total Liabilities $ — $ 13,010 $ — $ 13,010 We classify financial instruments as Level 3 when valuation models are used because significant inputs are not observable in the market. We may be required to measure certain assets and liabilities on a nonrecurring basis. Nonrecurring assets are recorded at the lower of cost or fair value in our financial statements. There were no liabilities measured at fair value on a nonrecurring basis at December 31, 2015 and 2014. The following table presents our assets that are measured at fair value on a nonrecurring basis by the fair value hierarchy level as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total ASSETS (1) Impaired loans — — 9,373 9,373 — — 12,916 12,916 Other real estate owned — — 158 158 — — 117 117 Mortgage servicing rights — — 3,396 3,396 — — 2,934 2,934 Total Assets $ — $ — $ 12,927 $ 12,927 $ — $ — $ 15,967 $ 15,967 (1) This table presents only the nonrecurring items that are recorded at fair value in our financial statements. The carrying values and fair values of our financial instruments at December 31, 2015 and 2014 are presented in the following tables: Fair Value Measurements at December 31, 2015 (dollars in thousands) Carrying Value (1) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 99,399 $ 99,399 $ 99,399 $ — $ — Securities available-for-sale 660,963 660,963 — 660,963 — Loans held for sale 35,321 35,500 — — 35,500 Portfolio loans, net of unearned income 5,027,612 5,001,004 — — 5,001,004 Bank owned life insurance 70,175 70,175 — 70,175 — FHLB and other restricted stock 23,032 23,032 — — 23,032 Trading securities held in a Rabbi Trust 4,021 4,021 4,021 — — Mortgage servicing rights 3,237 3,396 — — 3,396 Interest rate swaps 11,295 11,295 — 11,295 — Interest rate lock commitments 261 261 — 261 — LIABILITIES Deposits $ 4,876,611 $ 4,881,718 $ — $ — $ 4,881,718 Securities sold under repurchase agreements 62,086 62,086 — — 62,086 Short-term borrowings 356,000 356,000 — — 356,000 Long-term borrowings 117,043 117,859 — — 117,859 Junior subordinated debt securities 45,619 45,619 — — 45,619 Interest rate swaps 11,276 11,276 — 11,276 — Forward sale contracts 5 5 — 5 — (1) As reported in the Consolidated Balance Sheets Fair Value Measurements at December 31, 2014 (dollars in thousands) Carrying Value (1) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 109,580 $ 109,580 $ 109,580 $ — $ — Securities available-for-sale 640,273 640,273 178 640,095 — Loans held for sale 2,970 2,991 — — 2,991 Portfolio loans, net of unearned income 3,868,746 3,827,634 — — 3,827,634 Bank owned life insurance 62,252 62,252 — 62,252 — FHLB and other restricted stock 15,135 15,135 — — 15,135 Trading securities held in a Rabbi Trust 3,456 3,456 3,456 — — Mortgage servicing rights 2,817 2,934 — — 2,934 Interest rate swaps 12,981 12,981 — 12,981 — Interest rate lock commitments 235 235 — 235 — LIABILITIES Deposits $ 3,908,842 $ 3,910,342 $ — $ — $ 3,910,342 Securities sold under repurchase agreements 30,605 30,605 — — 30,605 Short-term borrowings 290,000 290,000 — — 290,000 Long-term borrowings 19,442 20,462 — — 20,462 Junior subordinated debt securities 45,619 45,619 — — 45,619 Interest rate swaps 12,953 12,953 — 12,953 — Forward sale contracts 57 57 — 57 — (1) As reported in the Consolidated Balance Sheets

Restrictions on Cash and Due fr

Restrictions on Cash and Due from Bank Accounts	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Restrictions on Cash and Due from Bank Accounts	RESTRICTIONS ON CASH AND DUE FROM BANK ACCOUNTS The Board of Governors of the Federal Reserve System, or the Federal Reserve, imposes certain reserve requirements on all depository institutions. These reserves are maintained in the form of vault cash or as an interest-bearing balance with the Federal Reserve. The required reserves averaged $44.1 million for the year ended 2015, $41.8 million for the year ended 2014 and $39.7 million for the year ended 2013.

Dividend and Loan Restrictions

Dividend and Loan Restrictions	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Dividend and Loan Restrictions	DIVIDEND AND LOAN RESTRICTIONS S&T is a legal entity separate and distinct from its banking and other subsidiaries. A substantial portion of our revenues consist of dividend payments we receive from S&T Bank. S&T Bank, in turn, is subject to state laws and regulations that limit the amount of dividends it can pay to us. In addition, both S&T and S&T Bank are subject to various general regulatory policies relating to the payment of dividends, including requirements to maintain adequate capital above regulatory minimums. The Federal Reserve has indicated that banking organizations should generally pay dividends only if (i) the organization’s net income available to common shareholders over the past year has been sufficient to fully fund the dividends and (ii) the prospective rate of earnings retention appears consistent with the organization’s capital needs, asset quality and overall financial condition. Thus, under certain circumstances based upon our financial condition, our ability to declare and pay quarterly dividends may require consultation with the Federal Reserve and may be prohibited by applicable Federal Reserve guidelines. Federal law prohibits us from borrowing from S&T Bank unless such loans are collateralized by specific obligations. Further, such loans are limited to 10 percent of S&T Bank’s capital stock and surplus.

Securities Available-for-Sale

Securities Available-for-Sale	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Securities Available-for-Sale	SECURITIES AVAILABLE-FOR-SALE The following tables present the amortized cost and fair value of available-for-sale securities as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 14,914 $ 27 $ — $ 14,941 $ 14,873 $ 7 $ — $ 14,880 Obligations of U.S. government corporations and agencies 262,045 1,825 (567 ) 263,303 268,029 2,334 (1,078 ) 269,285 Collateralized mortgage obligations of U.S. government corporations and agencies 128,458 693 (316 ) 128,835 116,897 1,257 (148 ) 118,006 Residential mortgage-backed securities of U.S. government corporations and agencies 39,185 1,091 (151 ) 40,125 45,274 1,548 (154 ) 46,668 Commercial mortgage-backed securities of U.S. government corporations and agencies 69,697 183 (676 ) 69,204 39,834 232 (393 ) 39,673 Obligations of states and political subdivisions 128,904 5,988 (6 ) 134,886 136,977 5,789 (64 ) 142,702 Debt Securities 643,203 9,807 (1,716 ) 651,294 621,884 11,167 (1,837 ) 631,214 Marketable equity securities 7,579 2,090 — 9,669 7,579 1,480 — 9,059 Total $ 650,782 $ 11,897 $ (1,716 ) $ 660,963 $ 629,463 $ 12,647 $ (1,837 ) $ 640,273 The following table shows the composition of gross and net realized gains and losses for the periods presented: Years ended December 31, (dollars in thousands) 2015 2014 2013 Gross realized gains $ — $ 41 $ 5 Gross realized losses (34 ) — — Net Realized (Losses) Gains $ (34 ) $ 41 $ 5 The following tables present the fair value and the age of gross unrealized losses by investment category as of the dates presented: December 31, 2015 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Losses Number of Securities Fair Unrealized Losses Number of Securities Fair Unrealized Losses Obligations of U.S. government corporations and agencies 10 $ 88,584 $ (379 ) 2 $ 14,542 $ (188 ) 12 $ 103,126 $ (567 ) Collateralized mortgage obligations of U.S. government corporations and agencies 6 61,211 (316 ) — — — 6 61,211 (316 ) Residential mortgage-backed securities of U.S. government corporations and agencies 1 7,993 (151 ) — — — 1 7,993 (151 ) Commercial mortgage-backed securities of U.S. government corporations and agencies 5 50,839 (450 ) 1 9,472 (226 ) 6 60,311 (676 ) Obligations of states and political subdivisions 1 5,370 (6 ) — — — 1 5,370 (6 ) Total Temporarily Impaired Securities 23 $ 213,997 $ (1,302 ) 3 $ 24,014 $ (414 ) 26 $ 238,011 $ (1,716 ) December 31, 2014 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses Obligations of U.S. government corporations and agencies 4 $ 39,745 $ (207 ) 8 $ 63,149 $ (871 ) 12 $ 102,894 $ (1,078 ) Collateralized mortgage obligations of U.S. government corporations and agencies 1 9,323 (148 ) — — — 1 9,323 (148 ) Residential mortgage-backed securities of U.S. government corporations and agencies — — — 1 8,982 (154 ) 1 8,982 (154 ) Commercial mortgage-backed securities of U.S. government corporations and agencies 1 9,998 (25 ) 2 20,640 (368 ) 3 30,638 (393 ) Obligations of states and political subdivisions 1 263 (1 ) 2 10,756 (63 ) 3 11,019 (64 ) Total Temporarily Impaired Securities 7 $ 59,329 $ (381 ) 13 $ 103,527 $ (1,456 ) 20 $ 162,856 $ (1,837 ) We do not believe any individual unrealized loss as of December 31, 2015 represents an other than temporary impairment, or OTTI. As of December 31, 2015, the unrealized losses on 26 debt securities were primarily attributable to changes in interest rates and not related to the credit quality of these securities. All debt securities are determined to be investment grade and are paying principal and interest according to the contractual terms of the security. There were no unrealized losses on marketable equity securities at either December 31, 2015 or 2014. We do not intend to sell and it is more likely than not that we will not be required to sell any of the securities in an unrealized loss position before recovery of their amortized cost. The following table displays net unrealized gains and losses, net of tax on securities available for sale included in accumulated other comprehensive income/(loss) for the periods presented: December 31, 2015 December 31, 2014 (dollars in thousands) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains (Losses) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains (Losses) Total unrealized gains (losses) on securities available for sale $ 11,897 $ (1,716 ) $ 10,181 $ 12,647 $ (1,837 ) $ 10,810 Income tax expense (benefit) 4,164 (601 ) 3,563 4,426 (643 ) 3,783 Net unrealized gains (losses), net of tax included in accumulated other comprehensive income(loss) $ 7,733 $ (1,115 ) $ 6,618 $ 8,221 $ (1,194 ) $ 7,027 The amortized cost and fair value of securities available-for-sale at December 31, 2015 by contractual maturity are included in the table below. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. December 31, 2015 (dollars in thousands) Amortized Cost Fair Value Due in one year or less $ 46,329 $ 46,510 Due after one year through five years 222,838 224,334 Due after five years through ten years 56,934 58,793 Due after ten years 79,762 83,493 405,863 413,130 Collateralized mortgage obligations of U.S. government corporations and agencies 128,458 128,835 Residential mortgage-backed securities of U.S. government corporations and agencies 39,185 40,125 Commercial mortgage-backed securities of U.S. government corporations and agencies 69,697 69,204 Debt Securities 643,203 651,294 Marketable equity securities 7,579 9,669 Total $ 650,782 $ 660,963 At December 31, 2015 and 2014, securities with carrying values of $278.4 million and $289.1 million were pledged for various regulatory and legal requirements.

Loans and Loans Held for Sale

Loans and Loans Held for Sale	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Loans and Loans Held for Sale	LOANS AND LOANS HELD FOR SALE Loans are presented net of unearned income of $3.2 million and $2.1 million at December 31, 2015 and 2014 and net of a discount related to purchase accounting fair value adjustments of $10.9 million and $2.0 million at December 31, 2015 and December 31, 2014. The following table indicates the composition of the acquired and originated loans as of the dates presented: December 31, (dollars in thousands) 2015 2014 Commercial Commercial real estate $ 2,166,603 $ 1,682,236 Commercial and industrial 1,256,830 994,138 Commercial construction 413,444 216,148 Total Commercial Loans 3,836,877 2,892,522 Consumer Residential mortgage 639,372 489,586 Home equity 470,845 418,563 Installment and other consumer 73,939 65,567 Consumer construction 6,579 2,508 Total Consumer Loans 1,190,735 976,224 Total Portfolio Loans 5,027,612 3,868,746 Loans held for sale 35,321 2,970 Total Loans $ 5,062,933 $ 3,871,716 As of December 31, 2015, our acquired loans from the Merger were $673.3 million including $293.2 million of CRE, $167.7 million of C&I, $69.2 million of commercial construction, $115.6 million of residential mortgage, $27.5 million of home equity, installment and other consumer construction. These acquired loans decreased from the original fair value on March, 2015 of $788.7 million , including $331.6 million of CRE, $184.2 million of C&I, $92.4 million of commercial construction, $116.9 million of residential mortgage, $25.6 million of home equity, $36.1 million of installment and other consumer and $1.9 million of consumer construction. As of December 31, 2015, we had $35.3 million of loans held for sale, which included $23.3 million related to the decision to sell our credit card portfolio and the remaining balance related to mortgages held for sale. We attempt to limit our exposure to credit risk by diversifying our loan portfolio by segment, geography, collateral and industry and actively managing concentrations. When concentrations exist in certain segments, we mitigate this risk by monitoring the relevant economic indicators and internal risk rating trends and through stress testing of the loans in these segments. Total commercial loans represented 76 percent of total portfolio loans at December 31, 2015 and 75 percent of total portfolio loans at December 31, 2014. Within our commercial portfolio, the CRE and Commercial Construction portfolios combined comprised $2.6 billion or 67 percent of total commercial loans and 51 percent of total portfolio loans at December 31, 2015 and 66 percent of total commercial loans and 49 percent of total portfolio loans at December 31, 2014. Of the $2.6 billion of CRE and Commercial Construction loans, $424.0 million were added as a result of the Merger. Further segmentation of the CRE and Commercial Construction portfolios by industry and collateral type reveal no concentration in excess of seven percent of total loans at either December 31, 2015 or December 31, 2014. Our market area includes Pennsylvania and the contiguous states of Ohio, West Virginia, New York and Maryland. The majority of our commercial and consumer loans are made to businesses and individuals in this market area resulting in a geographic concentration. We believe our knowledge and familiarity with customers and conditions locally outweighs this geographic concentration risk. The conditions of the local and regional economies are monitored closely through publicly available data as well as information supplied by our customers. Management believes underwriting guidelines, active monitoring of economic conditions and ongoing review by credit administration mitigates the concentration risk present in the loan portfolio. Our CRE and Commercial Construction portfolios have out-of-market exposure of 5.8 percent of the combined portfolio and 3.0 percent of total loans at December 31, 2015 and 8.0 percent of the combined portfolio and 3.9 percent of total loans at December 31, 2014. TDRs are loans where we, for economic or legal reasons related to a borrower's financial difficulties, grant a concession to the borrower that we would not otherwise grant. We strive to identify borrowers in financial difficulty early and work with them to modify the terms before their loan reaches nonaccrual status. These modified terms generally include extensions of maturity dates at a stated interest rate lower than the current market rate for a new loan with similar risk characteristics, reductions in contractual interest rates or principal deferment. While unusual, there may be instances of principal forgiveness. These modifications are generally for longer term periods that would not be considered insignificant. Additionally, we classify loans where the debt obligation has been discharged through a Chapter 7 Bankruptcy and not reaffirmed as TDRs. We individually evaluate all substandard commercial loans that have experienced a forbearance or change in terms agreement, as well as all substandard consumer and residential mortgage loans that entered into an agreement to modify their existing loan to determine if they should be designated as TDRs. All TDRs are considered to be impaired loans and will be reported as impaired loans for the remaining life of the loan, unless the restructuring agreement specifies an interest rate equal to or greater than the rate that would be accepted at the time of the restructuring for a new loan with comparable risk and it is fully expected that the remaining principal and interest will be collected according to the restructured agreement. Further, all impaired loans are reported as nonaccrual loans unless the loan is a TDR that has met the requirements to be returned to accruing status. TDRs can be returned to accruing status if the ultimate collectability of all contractual amounts due, according to the restructured agreement, is not in doubt and there is a period of a minimum of six months of satisfactory payment performance by the borrower either immediately before or after the restructuring. The following table summarizes the restructured loans as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Performing TDRs Nonperforming TDRs Total TDRs Performing TDRs Nonperforming TDRs Total TDRs Commercial real estate $ 6,822 $ 3,548 $ 10,370 $ 16,939 $ 2,180 $ 19,119 Commercial and industrial 6,321 1,570 7,891 8,074 356 8,430 Commercial construction 5,013 1,265 6,278 5,736 1,869 7,605 Residential mortgage 2,590 665 3,255 2,839 459 3,298 Home equity 3,184 523 3,707 3,342 562 3,904 Installment and other consumer 25 88 113 53 10 63 Total $ 23,955 $ 7,659 $ 31,614 $ 36,983 $ 5,436 $ 42,419 The following tables present the restructured loans for the 12 months ended December 31: 2015 (dollars in thousands) Number of Loans Pre-Modification Outstanding Recorded Investment (1) Post-Modification Outstanding Recorded Investment (1) Total Difference in Recorded Investment Commercial real estate Principal deferral 2 $ 2,851 $ 1,841 $ (1,010 ) Maturity date extension 3 438 427 (11 ) Commercial and industrial Principal deferral 6 661 363 (298 ) Maturity date extension 2 824 728 (96 ) Commercial construction Maturity date extension 3 1,434 1,432 (2 ) Residential mortgage Maturity date extension 8 545 265 (280 ) Maturity date extension and interest rate reduction 1 207 205 (2 ) Chapter 7 bankruptcy (2) 7 428 226 (202 ) Home equity Maturity date extension 1 71 70 (1 ) Maturity date extension and interest rate reduction 3 203 201 (2 ) Chapter 7 bankruptcy (2) 23 619 576 (43 ) Installment and other consumer Chapter 7 bankruptcy (2) 1 9 4 (5 ) Total by Concession Type Principal deferral 8 3,512 2,204 (1,308 ) Maturity date extension and interest rate reduction 4 410 406 (4 ) Maturity date extension 17 3,312 2,922 (390 ) Chapter 7 bankruptcy (2) 31 1,056 806 (250 ) Total 60 $ 8,290 $ 6,338 $ (1,952 ) (1) Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Chapter 7 bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed. 2014 (dollars in thousands) Number of Loans Pre-Modification Outstanding Recorded Investment ( 1) Post-Modification Outstanding Recorded Investment (1 ) Total Difference in Recorded Investment Commercial real estate Principal deferral 4 $ 1,991 $ 1,965 $ (26 ) Commercial and industrial Principal deferral 2 381 356 (25 ) Commercial construction Maturity date extension 1 1,019 974 (45 ) Residential mortgage Chapter 7 bankruptcy (2) 9 651 634 (17 ) Home Equity Maturity date extension and interest rate reduction 2 96 95 (1 ) Maturity date extension 6 349 348 (1 ) Chapter 7 bankruptcy (2) 15 432 382 (50 ) Installment and other consumer Chapter 7 bankruptcy (2) 5 30 23 (7 ) Total by Concession Type Principal deferral 6 2,372 2,321 (51 ) Maturity date extension and interest rate reduction 2 96 95 (1 ) Maturity date extension 7 1,368 1,322 (46 ) Chapter 7 bankruptcy (2) 29 1,113 1,039 (74 ) Total 44 $ 4,949 $ 4,777 $ (172 ) (1) Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Chapter 7 bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed. During 2015, we modified 39 loans that were not considered to be TDRs, including 11 C&I loans for $7.8 million , 14 Commercial Construction loans for $8.5 million , eight CRE loans for $6.1 million , four Home Equity loans for $0.4 million and two Residential Real Estate loans for $0.1 million . The modifications primarily represented instances where we were adequately compensated through additional collateral or a higher interest rate or there was an insignificant delay in payment. As of December 31, 2015, we have no commitments to lend additional funds on any TDRs. We returned eight TDRs to accruing status during the twelve months ended December 31, 2015 totaling $0.4 million . We returned nine TDRs to accruing status during 2014 totaling $1.9 million . Defaulted TDRs are defined as loans having a payment default of 90 days or more after the restructuring takes place. The following tables present a summary of TDRs which defaulted during the years ended December 31, 2015 and 2014 that had been restructured within the last 12 months prior to defaulting: Defaulted TDRs For the For the (dollars in thousands) Number of Defaults Recorded Investment Number of Defaults Recorded Investment Commercial real estate — $ — — $ — Commercial and industrial — — — — Residential real estate — — 1 20 Home equity — — 2 44 Total — $ — 3 $ 64 The following table is a summary of nonperforming assets as of the dates presented: December 31, (dollars in thousands) 2015 2014 Nonperforming Assets Nonaccrual loans $ 27,723 $ 7,021 Nonaccrual TDRs 7,659 5,436 Total nonaccrual loans 35,382 12,457 OREO 354 166 Total Nonperforming Assets $ 35,736 $ 12,623 The increase in NPAs during 2015 was primarily due to subsequent deterioration on acquired loans since the acquisition date and a $4.7 million C&I loan. Included in the total NPAs of $35.7 million is approximately $16.3 million of loans from the Merger. We have granted loans to certain officers and directors of S&T as well as to certain affiliates of the officers and directors in the ordinary course of business. These loans were made on substantially the same terms, including interest rates and collateral, as those prevailing at the time for comparable transactions with unrelated persons and did not involve more than normal risk of collectability. The following table presents a summary of the aggregate amount of loans to any such persons as of December 31: (dollars in thousands) 2015 2014 Balance at beginning of year $ 27,368 $ 23,848 New loans 24,743 27,799 Repayments (27,594 ) (24,279 ) Balance at End of Year $ 24,517 $ 27,368

Allowance for Loan Losses

Allowance for Loan Losses	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Allowance for Loan Losses	ALLOWANCE FOR LOAN LOSSES We maintain an ALL at a level determined to be adequate to absorb estimated probable credit losses inherent in the loan portfolio as of the balance sheet date. We develop and document a systematic ALL methodology based on the following portfolio segments: 1) CRE, 2) C&I, 3) Commercial Construction, 4) Consumer Real Estate and 5) Other Consumer. The following are key risks within each portfolio segment: CRE —Loans secured by commercial purpose real estate, including both owner occupied properties and investment properties for various purposes such as hotels, strip malls and apartments. Operations of the individual projects as well as global cash flows of the debtors are the primary sources of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type as well as the business prospects of the lessee, if the project is not owner occupied. C&I —Loans made to operating companies or manufacturers for the purpose of production, operating capacity, accounts receivable, inventory or equipment financing. Cash flow from the operations of the company is the primary source of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the industry of the company. Collateral for these types of loans often do not have sufficient value in a distressed or liquidation scenario to satisfy the outstanding debt. Commercial Construction —Loans made to finance construction of buildings or other structures, as well as to finance the acquisition and development of raw land for various purposes. While the risk of these loans is generally confined to the construction period, if there are problems, the project may not be complete, and as such, may not provide sufficient cash flow on its own to service the debt or have sufficient value in a liquidation to cover the outstanding principal. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the type of project and the experience and resources of the developer. Consumer Real Estate —Loans secured by first and second liens such as home equity loans, home equity lines of credit and 1-4 family residences, including purchase money mortgages. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The state of the local housing market can also have a significant impact on this segment because low demand and/or declining home values can limit the ability of borrowers to sell a property and satisfy the debt. Other Consumer —Loans made to individuals that may be secured by assets other than 1-4 family residences, as well as unsecured loans. This segment includes auto loans, unsecured loans and lines and credit cards. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The value of the collateral, if there is any, is less likely to be a source of repayment due to less certain collateral values. We further assess risk within each portfolio segment by pooling loans with similar risk characteristics. For the commercial loan classes, the most important indicator of risk is the internally assigned risk rating, including pass, special mention and substandard. Consumer loans are pooled by type of collateral, lien position and LTV ratio for Consumer Real Estate loans. Historical loss rates are applied to these loan pools to determine the reserve for loans collectively evaluated for impairment. The ALL methodology for groups of loans collectively evaluated for impairment is comprised of both a quantitative and qualitative analysis. A key assumption in the quantitative component of the reserve is LEP. The LEP is an estimate of the average amount of time from the point at which a loss is incurred on a loan to the point at which the loss is confirmed. Another key assumption is LBP, which represents the historical data period utilized to calculate loss rates. Management monitors various credit quality indicators for both the commercial and consumer loan portfolios, including delinquency, nonperforming status and changes in risk ratings on a monthly basis. The following tables present the age analysis of past due loans segregated by class of loans as of the dates presented: December 31, 2015 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due Non- performing Total Past Due Loans Total Loans Commercial real estate $ 2,145,655 $ 11,602 $ 627 $ 8,719 $ 20,948 $ 2,166,603 Commercial and industrial 1,244,802 2,453 296 9,279 12,028 1,256,830 Commercial construction 401,084 3,517 90 8,753 12,360 413,444 Residential mortgage 631,085 1,728 930 5,629 8,287 639,372 Home equity 465,055 2,365 523 2,902 5,790 470,845 Installment and other consumer 73,486 242 111 100 453 73,939 Consumer construction 6,579 — — — — 6,579 Loans held for sale 35,179 94 48 — 142 35,321 Total $ 5,002,925 $ 22,001 $ 2,625 $ 35,382 $ 60,008 $ 5,062,933 December 31, 2014 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due Non- performing Total Past Due Loans Total Loans Commercial real estate $ 1,674,930 $ 2,548 $ 323 $ 4,435 $ 7,306 $ 1,682,236 Commercial and industrial 991,136 1,227 153 1,622 3,002 994,138 Commercial construction 214,174 — — 1,974 1,974 216,148 Residential mortgage 485,465 565 1,220 2,336 4,121 489,586 Home equity 414,303 1,756 445 2,059 4,260 418,563 Installment and other consumer 65,111 352 73 31 456 65,567 Consumer construction 2,508 — — — — 2,508 Loans held for sale 2,970 — — — — 2,970 Total $ 3,850,597 $ 6,448 $ 2,214 $ 12,457 $ 21,119 $ 3,871,716 We continually monitor the commercial loan portfolio through an internal risk rating system. Loan risk ratings are assigned based upon the creditworthiness of the borrower and are reviewed on an ongoing basis according to our internal policies. Loans within the pass rating generally have a lower risk of loss than loans risk rated as special mention and substandard. Our risk ratings are consistent with regulatory guidance and are as follows: Pass —The loan is currently performing and is of high quality. Special Mention —A special mention loan has potential weaknesses that warrant management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects or in the strength of our credit position at some future date. Economic and market conditions, beyond the borrower’s control, may in the future necessitate this classification. Substandard —A substandard loan is not adequately protected by the net worth and/or paying capacity of the borrower or by the collateral pledged, if any. Substandard loans have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. These loans are characterized by the distinct possibility that we will sustain some loss if the deficiencies are not corrected. The following tables present the recorded investment in commercial loan classes by internally assigned risk ratings as of the dates presented: December 31, 2015 (dollars in thousands) Commercial Real Estate % of Total Commercial and Industrial % of Total Commercial Construction % of Total Total % of Total Pass $ 2,094,851 96.7 % $ 1,182,685 94.1 % $ 375,808 90.9 % $ 3,653,344 95.2 % Special mention 19,938 0.9 % 43,896 3.5 % 19,846 4.8 % 83,680 2.2 % Substandard 51,814 2.4 % 30,249 2.4 % 17,790 4.3 % 99,853 2.6 % Total $ 2,166,603 100.0 % $ 1,256,830 100.0 % $ 413,444 100.0 % $ 3,836,877 100.0 % December 31, 2014 (dollars in thousands) Commercial Real Estate % of Total Commercial and Industrial % of Total Commercial Construction % of Total Total % of Total Pass $ 1,635,132 97.2 % $ 948,663 95.4 % $ 196,520 90.9 % $ 2,780,315 96.1 % Special mention 23,597 1.4 % 30,357 3.1 % 12,014 5.6 % 65,968 2.3 % Substandard 23,507 1.4 % 15,118 1.5 % 7,614 3.5 % 46,239 1.6 % Total $ 1,682,236 100.0 % $ 994,138 100.0 % $ 216,148 100.0 % $ 2,892,522 100.0 % We monitor the delinquent status of the consumer portfolio on a monthly basis. Loans are considered nonperforming when interest and principal are 90 days or more past due or management has determined that a material deterioration in the borrower’s financial condition exists. The risk of loss is generally highest for nonperforming loans. The following tables present the recorded investment in consumer loan classes by performing and nonperforming status as of the dates presented: December 31, 2015 (dollars in thousands) Residential Mortgage % of Total Home Equity % of Total Installment and other consumer % of Total Consumer Construction % of Total Total % of Total Performing $ 633,743 99.1 % $ 467,943 99.4 % $ 73,839 99.8 % $ 6,579 100.0 % $ 1,182,104 99.3 % Nonperforming 5,629 0.9 % 2,902 0.6 % 100 0.2 % — — % 8,631 0.7 % Total $ 639,372 100.0 % $ 470,845 100.0 % $ 73,939 100.0 % $ 6,579 100.0 % $ 1,190,735 100.0 % December 31, 2014 (dollars in thousands) Residential Mortgage % of Total Home Equity % of Total Installment and other consumer % of Total Consumer Construction % of Total Total % of Total Performing $ 487,250 99.5 % $ 416,504 99.5 % $ 65,536 99.9 % $ 2,508 100.0 % $ 971,798 99.5 % Nonperforming 2,336 0.5 % 2,059 0.5 % 31 0.1 % — — % 4,426 0.5 % Total $ 489,586 100.0 % $ 418,563 100.0 % $ 65,567 100.0 % $ 2,508 100.0 % $ 976,224 100.0 % We individually evaluate all substandard and nonaccrual commercial loans greater than $0.5 million for impairment. Loans are considered to be impaired when based upon current information and events it is probable that we will be unable to collect all principal and interest payments due according to the original contractual terms of the loan agreement. All TDRs will be reported as an impaired loan for the remaining life of the loan, unless the restructuring agreement specifies an interest rate equal to or greater than the rate that would be accepted at the time of the restructuring for a new loan with comparable risk and it is expected that the remaining principal and interest will be fully collected according to the restructured agreement. For all TDRs, regardless of size, as well as all other impaired loans, we conduct further analysis to determine the probable loss and assign a specific reserve to the loan if deemed appropriate. The following tables summarize investments in loans considered to be impaired and related information on those impaired loans as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Recorded Investment Unpaid Principal Balance Related Allowance Recorded Investment Unpaid Principal Balance Related Allowance With a related allowance recorded: Commercial real estate $ — $ — $ — $ — $ — $ — Commercial and industrial — — — — — — Commercial construction 500 1,350 3 — — — Consumer real estate 116 116 32 43 43 43 Other consumer 2 2 2 20 20 11 Total with a Related Allowance Recorded 618 1,468 37 63 63 54 Without a related allowance recorded: Commercial real estate 12,661 13,157 — 19,890 25,262 — Commercial and industrial 14,417 15,220 — 9,218 9,449 — Commercial construction 10,998 14,200 — 7,605 11,293 — Consumer real estate 6,845 7,521 — 7,159 7,733 — Other consumer 111 188 — 42 48 — Total without a Related Allowance Recorded 45,032 50,286 — 43,914 53,785 — Total: Commercial real estate 12,661 13,157 — 19,890 25,262 — Commercial and industrial 14,417 15,220 — 9,218 9,449 — Commercial construction 11,498 15,550 3 7,605 11,293 — Consumer real estate 6,961 7,637 32 7,202 7,776 43 Other consumer 113 190 2 62 68 11 Total $ 45,650 $ 51,754 $ 37 $ 43,977 $ 53,848 $ 54 As of December 31, 2015, we had $45.7 million of impaired loans which included $9.9 million of acquired loans that experienced credit deterioration since the acquisition date. The following table summarizes investments in loans considered to be impaired and related information on those impaired loans for the years presented: For the Year Ended December 31, 2015 December 31, 2014 (dollars in thousands) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized With a related allowance recorded: Commercial real estate $ — $ — $ — $ — Commercial and industrial — — — — Commercial construction 834 — — — Consumer real estate 120 7 48 4 Other consumer 2 — 24 2 Total with a Related Allowance Recorded 956 7 72 6 Without a related allowance recorded: Commercial real estate 14,622 597 20,504 684 Commercial and industrial 14,416 450 9,246 241 Commercial construction 10,581 329 8,145 227 Consumer real estate 6,902 364 7,027 396 Other consumer 117 1 56 2 Total without a Related Allowance Recorded 46,638 1,741 44,978 1,550 Total: Commercial real estate 14,622 597 20,504 684 Commercial and industrial 14,416 450 9,246 241 Commercial construction 11,415 329 8,145 227 Consumer real estate 7,022 371 7,075 400 Other consumer 119 1 80 4 Total $ 47,594 $ 1,748 $ 45,050 $ 1,556 The following tables detail activity in the ALL for the periods presented: 2015 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Consumer Real Estate Other Consumer Total Loans Balance at beginning of year $ 20,164 $ 13,668 $ 6,093 $ 6,333 $ 1,653 $ 47,911 Charge-offs (2,787 ) (5,463 ) (3,321 ) (2,167 ) (1,528 ) (15,266 ) Recoveries 3,545 605 143 495 326 5,114 Net Recoveries (Charge-offs) 758 (4,858 ) (3,178 ) (1,672 ) (1,202 ) (10,152 ) Provision for loan losses (5,879 ) 2,043 9,710 3,739 775 10,388 Balance at End of Year $ 15,043 $ 10,853 $ 12,625 $ 8,400 $ 1,226 $ 48,147 2014 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Consumer Real Estate Other Consumer Total Loans Balance at beginning of year $ 18,921 $ 14,433 $ 5,374 $ 6,362 $ 1,165 $ 46,255 Charge-offs (2,041 ) (1,267 ) (712 ) (1,200 ) (1,133 ) (6,353 ) Recoveries 1,798 3,647 146 350 353 6,294 Net (Charge-offs)/ Recoveries (243 ) 2,380 (566 ) (850 ) (780 ) (59 ) Provision for loan losses 1,486 (3,145 ) 1,285 821 1,268 1,715 Balance at End of Year $ 20,164 $ 13,668 $ 6,093 $ 6,333 $ 1,653 $ 47,911 Loans acquired in the Merger were recorded at fair value with no carryover of the ALL. As of December 31, 2015, acquired loans from the Merger of $673.3 million were outstanding, which decreased from $788.7 million at the Merger date. Additional credit deterioration on acquired loans during 2015, in excess of the original credit discount embedded in the fair value determination on the date of acquisition, was recognized in the ALL through the provision for loan losses. The following tables present the ALL and recorded investments in loans by category as of December 31: 2015 Allowance for Loan Losses Portfolio Loans (dollars in thousands) Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Commercial real estate $ — $ 15,043 $ 15,043 $ 12,661 $ 2,153,942 $ 2,166,603 Commercial and industrial — 10,853 10,853 14,417 1,242,413 1,256,830 Commercial construction 3 12,622 12,625 11,498 401,946 413,444 Consumer real estate 32 8,368 8,400 6,961 1,109,835 1,116,796 Other consumer 2 1,224 1,226 113 73,826 73,939 Total $ 37 $ 48,110 $ 48,147 $ 45,650 $ 4,981,962 $ 5,027,612 2014 Allowance for Loan Losses Portfolio Loans (dollars in thousands) Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Commercial real estate $ — $ 20,164 $ 20,164 $ 19,890 $ 1,662,346 $ 1,682,236 Commercial and industrial — 13,668 13,668 9,218 984,920 994,138 Commercial construction — 6,093 6,093 7,605 208,543 216,148 Consumer real estate 43 6,290 6,333 7,202 903,455 910,657 Other consumer 11 1,642 1,653 62 65,505 65,567 Total $ 54 $ 47,857 $ 47,911 $ 43,977 $ 3,824,769 $ 3,868,746

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Premises and Equipment	PREMISES AND EQUIPMENT The following table is a summary of premises and equipment as of the dates presented: December 31, (dollars in thousands) 2015 2014 Land $ 8,699 $ 6,193 Premises 52,968 44,690 Furniture and equipment 29,543 26,661 Leasehold improvements 7,186 6,545 98,396 84,089 Accumulated depreciation (49,269 ) (45,923 ) Total $ 49,127 $ 38,166 Depreciation expense related to premises and equipment was $4.7 million in 2015, $3.5 million in 2014 and $3.5 million in 2013. Certain banking facilities are leased under arrangements expiring at various dates until the year 2054 . We account for these leases on a straight-line basis due to escalation clauses. All leases are accounted for as operating leases, except for one capital lease. Rental expense for premises amounted to $3.9 million , $2.7 million and $2.5 million in 2015, 2014 and 2013. Included in the rental expense for premises are leases entered into with two S&T directors, which totaled $0.2 million each year in 2015, 2014 and 2013. Minimum annual rental and renewal option payments for each of the following five years and thereafter are approximately: (dollars in thousands) Operating Capital Total 2016 $ 2,860 $ 76 $ 2,936 2017 2,895 76 2,971 2018 2,899 76 2,975 2019 2,913 77 2,990 2020 2,857 77 2,934 Thereafter 53,107 610 53,717 Total $ 67,531 $ 992 $ 68,523

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	GOODWILL AND OTHER INTANGIBLE ASSETS The following table presents goodwill as of the dates presented: December 31, (dollars in thousands) 2015 2014 Balance at beginning of year $ 175,820 $ 175,820 Additions 115,944 — Balance at End of Year $ 291,764 $ 175,820 Goodwill represents the excess of the purchase price over the fair value of net assets acquired. Additional goodwill of $115.9 million was recorded during 2015, for our acquisition of Integrity. Refer to Note 2 Business Combinations for further details on the Integrity acquisition. There were no additions to goodwill in 2014. Goodwill is reviewed for impairment annually or more frequently if it is determined that a triggering event has occurred. Based upon our qualitative assessment performed for our annual impairment analysis, we concluded that it is more likely than not that the fair value of the reporting units exceeds the carrying value. In general, the overall macroeconomic conditions and more specifically the economic conditions of the banking industry have continued to improve. Additionally, our overall performance has improved and we did not identify any other facts and circumstances causing us to conclude that it is more likely than not that the fair value of the reporting units would be less than the carrying value. The following table shows a summary of intangible assets as of the dates presented: December 31, (dollars in thousands) 2015 2014 Gross carrying amount at beginning of year $ 16,401 $ 16,401 Additions 5,713 — Accumulated amortization (15,589 ) (13,770 ) Balance at End of Year $ 6,525 $ 2,631 Intangible assets as of December 31, 2015 consisted of $6.1 million for core deposits, $0.1 million for wealth management relationships and $0.4 million for insurance contract relationships resulting from acquisitions. The addition of $5.7 million during 2015 was due to the core deposit intangible asset related to the acquisition of Integrity. We determined the amount of identifiable intangible assets based upon independent core deposit, wealth management and insurance contract valuations. Other intangible assets are evaluated for impairment whenever events or changes in circumstances indicate that their carrying amounts may not be recoverable. There were no triggering events in 2015 requiring an impairment analysis to be completed. Amortization expense on finite-lived intangible assets totaled $1.8 million , $1.1 million and $1.6 million for 2015, 2014 and 2013. The following is a summary of the expected amortization expense for finite-lived intangibles assets, assuming no new additions, for each of the five years following December 31, 2015: (dollars in thousands) Amount 2016 $ 1,433 2017 1,149 2018 668 2019 561 2020 475 Total $ 4,286

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES The following table indicates the amount representing the value of derivative assets and derivative liabilities at December 31: Derivatives (included in Other Assets) Derivatives (included in Other Liabilities) (dollars in thousands) 2015 2014 2015 2014 Derivatives not Designated as Hedging Instruments Interest Rate Swap Contracts—Commercial Loans Fair value $ 11,295 $ 12,981 $ 11,276 $ 12,953 Notional amount 245,595 245,152 245,595 245,152 Collateral posted — — 12,753 12,059 Interest Rate Lock Commitments—Mortgage Loans Fair value 261 235 — — Notional amount 9,894 8,822 — — Forward Sale Contracts—Mortgage Loans Fair value — — 5 57 Notional amount — — 9,800 7,789 The following table indicates the gross amounts of commercial loan swap derivative assets and derivative liabilities, the amounts offset and the carrying values in the Consolidated Balance Sheets at December 31: Derivatives (included in Other Assets) Derivatives (included in Other Liabilities) (dollars in thousands) 2015 2014 2015 2014 Derivatives not Designated as Hedging Instruments Gross amounts recognized $ 11,295 $ 13,203 $ 11,276 $ 13,175 Gross amounts offset — (222 ) — (222 ) Net amounts presented in the Consolidated Balance Sheets 11,295 12,981 11,276 12,953 Gross amounts not offset (1) — — (12,573 ) (12,059 ) Net Amount $ 11,295 $ 12,981 $ (1,297 ) $ 894 (1) Amounts represent posted collateral. The following table indicates the gain or loss recognized in income on derivatives for the years ended December 31: (dollars in thousands) 2015 2014 2013 Derivatives not Designated as Hedging Instruments Interest rate swap contracts—commercial loans $ (8 ) $ (24 ) $ (174 ) Interest rate lock commitments—mortgage loans 26 150 (382 ) Forward sale contracts—mortgage loans 52 (90 ) 82 Total Derivative Gain (Loss) $ 70 $ 36 $ (474 )

Mortgage Servicing Rights

Mortgage Servicing Rights	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Mortgage Servicing Rights	MORTGAGE SERVICING RIGHTS For the years ended December 31, 2015, 2014 and 2013, the 1-4 family mortgage loans that were sold to Fannie Mae amounted to $76.8 million , $40.1 million and $62.9 million . At December 31, 2015, 2014 and 2013 our servicing portfolio totaled $361.2 million , $325.8 million and $327.4 million . The following table indicates MSRs and the net carrying values: (dollars in thousands) Servicing Rights Valuation Allowance Net Carrying Value Balance at December 31, 2013 $ 3,208 $ (289 ) $ 2,919 Additions 431 — 431 Amortization (531 ) — (531 ) Temporary (impairment) recapture — (2 ) (2 ) Balance at December 31, 2014 $ 3,108 $ (291 ) $ 2,817 Additions 856 — 856 Amortization (538 ) — (538 ) Temporary (impairment) recapture — 102 102 Balance at December 31, 2015 $ 3,426 $ (189 ) $ 3,237

Qualified Affordable Housing

Qualified Affordable Housing	12 Months Ended
	Dec. 31, 2015
Investments in Affordable Housing Projects [Abstract]
Qualified Affordable Housing Program	QUALIFIED AFFORDABLE HOUSING We invest in affordable housing projects primarily to satisfy our Community Reinvestment Act requirements. As a limited partner in these operating partnerships, we receive tax credits and tax deductions for losses incurred by the underlying properties. We use the cost method to account for these partnerships. Our total investment in qualified affordable housing projects was $15.0 million at December 31, 2015 and $18.6 million at December 31, 2014. We had no open commitments to fund current or future investments in qualified affordable housing projects at December 31, 2015 or December 31, 2014. Amortization expense, included in other noninterest expense in the Consolidated Statements of Net Income, was $3.6 million for December 31, 2015 and $4.1 million for both December 31, 2014 and 2013. Amortization expense was offset by tax credits of $4.0 million for December 31, 2015 and $4.3 million for both December 31, 2014 and 2013, as a reduction to our federal tax provision.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Deposits	DEPOSITS The following table presents the composition of deposits at December 31 and interest expense for the years ended December 31: 2015 2014 2013 (dollars in thousands) Balance Interest Expense Balance Interest Expense Balance Interest Expense Noninterest-bearing demand $ 1,227,766 $ — $ 1,083,919 $ — $ 992,779 $ — Interest-bearing demand 616,188 818 335,099 19 312,790 75 Money market 605,184 1,299 376,612 572 281,403 446 Savings 1,061,265 1,712 1,027,095 1,607 994,805 1,735 Certificates of deposit 1,366,208 9,115 1,086,117 7,930 1,090,531 9,150 Total $ 4,876,611 $ 12,944 $ 3,908,842 $ 10,128 $ 3,672,308 $ 11,406 The aggregate of all certificates of deposit over $100,000, including CDARS, amounted to $521.6 million and $382.2 million at December 31, 2015 and 2014. The following table indicates the scheduled maturities of certificates of deposit at December 31, 2015: (dollars in thousands) Amount 2016 $ 870,679 2017 304,820 2018 102,886 2019 37,742 2020 41,808 Thereafter 8,273 Total $ 1,366,208

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Short-Term Borrowings	SHORT-TERM BORROWINGS Short-term borrowings are for terms under one year and were comprised of REPOs and FHLB advances. REPOs are overnight short-term investments and are not insured by the Federal Deposit Insurance Corporation, or FDIC. Securities pledged as collateral under these REPO financing arrangements cannot be sold or repledged by the secured party and are therefore accounted for as a secured borrowing. Securities with a total carrying value of $67.0 million at December 31, 2015 and $35.6 million at December 31, 2014 were pledged as collateral for these secured transactions. The pledged securities are held in safekeeping at the Federal Reserve. Due to the overnight short-term nature of REPOs, potential risk due to a decline in the value of the pledged collateral is low. Collateral pledging requirements with REPOs are monitored daily. The following table represents the composition of short-term borrowings, the weighted average interest rate as of December 31 and interest expense for the years ended December 31: 2015 2014 2013 (dollars in thousands) Balance Weighted Average Interest Rate Interest Expense Balance Weighted Average Interest Rate Interest Expense Balance Weighted Average Interest Rate Interest Expense REPOs $ 62,086 0.01 % $ 4 $ 30,605 0.01 % $ 3 $ 33,847 0.01 % $ 62 FHLB advances 356,000 0.52 % 932 290,000 0.31 % 511 140,000 0.30 % 279 Total Short-term Borrowings $ 418,086 0.44 % $ 936 $ 320,605 0.27 % $ 514 $ 173,847 0.24 % $ 341

Long-Term Borrowings and Subord

Long-Term Borrowings and Subordinated Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Long-Term Borrowings and Subordinated Debt	LONG-TERM BORROWINGS AND SUBORDINATED DEBT Long-term borrowings are for original terms greater than or equal to one year and were comprised of FHLB advances, a capital lease and junior subordinated debt securities. Our long-term borrowings at the Pittsburgh FHLB were $117.0 million as of December 31, 2015 and $19.3 million as of December 31, 2014. FHLB borrowings are secured by a blanket lien on residential mortgages and other real estate secured loans. Total loans pledged as collateral at the FHLB were $2.8 billion at December 31, 2015. We were eligible to borrow up to an additional $1.4 billion based on qualifying collateral, to a maximum borrowing capacity of $1.9 billion at December 31, 2015. The following table represents the balance of long-term borrowings, the weighted average interest rate as of December 31 and interest expense for the years ended December 31: (dollars in thousand) 2015 2014 2013 Long-term borrowings $ 117,043 $ 19,442 $ 21,810 Weighted average interest rate 0.81 % 3.00 % 3.01 % Interest expense $ 790 $ 617 $ 746 Scheduled annual maturities and average interest rates for all of our long-term debt, including a capital lease of $0.2 million , for each of the five years and thereafter subsequent to December 31, 2015 are as follows: (dollars in thousands) Balance Average Rate 2016 $ 102,330 0.52 % 2017 2,412 3.52 % 2018 2,496 3.60 % 2019 2,514 3.13 % 2020 2,004 3.22 % Thereafter 5,287 1.85 % Total $ 117,043 0.81 % Junior Subordinated Debt Securities The following table represents the composition of junior subordinated debt securities at December 31 and the interest expense for the years ended December 31: 2015 2014 2013 (dollars in thousands) Balance Interest Expense Balance Interest Expense Balance Interest Expense 2006 Junior subordinated debt $ 25,000 $ 554 $ 25,000 $ 463 $ 25,000 $ 475 2008 Junior subordinated debt—trust preferred securities 20,619 773 20,619 759 20,619 770 2008 Junior subordinated debt — — — — — 422 2008 Junior subordinated debt — — — — — 403 Total $ 45,619 $ 1,327 $ 45,619 $ 1,222 $ 45,619 $ 2,070 The following table summarizes the key terms of our junior subordinated debt securities: (dollars in thousands) 2006 Junior Subordinated Debt 2008 Trust Preferred Securities 2008 Junior Subordinated Debt 2008 Junior Subordinated Debt Junior Subordinated Debt $25,000 — $20,000 $25,000 Trust Preferred Securities — $20,619 — — Stated Maturity Date 12/15/2036 3/15/2038 6/15/2018 5/30/2018 Optional redemption date at par Any time after 9/15/2011 Any time after 3/15/2013 Any time after 6/15/2013 Any time after 5/30/2013 Regulatory Capital Tier 2 Tier 1 Tier 2 Tier 2 Interest Rate 3 month LIBOR plus 160 bps 3 month LIBOR plus 350 bps 3 month LIBOR plus 350 bps 3 month LIBOR plus 250 bps Interest Rate at December 31, 2015 2.11% 4.01% —% —% We completed a private placement of the trust preferred securities to a financial institution during the first quarter of 2008. As a result, we own 100 percent of the common equity of STBA Capital Trust I. The trust was formed to issue mandatorily redeemable capital securities to third-party investors. The proceeds from the sale of the securities and the issuance of the common equity by STBA Capital Trust I were invested in junior subordinated debt securities issued by us. The third party investors are considered the primary beneficiaries; therefore, the trust qualifies as a VIE, but is not consolidated into our financial statements. STBA Capital Trust I pays dividends on the securities at the same rate as the interest paid by us on the junior subordinated debt held by STBA Capital Trust I. We repaid $45.0 million of junior subordinated debt in June of 2013 because of its diminishing regulatory capital benefit and the future positive impact on net interest income. We replaced the funding primarily with FHLB short-term advances. On March 4, 2015 we assumed a $13.5 million junior subordinated debt from the acquisition of Integrity. On March 5, 2015, we paid off $8.5 million and on June 18, 2015, we paid off the remaining $5.0 million .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Commitments The following table sets forth our commitments and letters of credit as of the dates presented: December 31, (dollars in thousands) 2015 2014 Commitments to extend credit $ 1,619,854 $ 1,158,628 Standby letters of credit 97,676 73,584 Total $ 1,717,530 $ 1,232,212 Estimates of the fair value of these off-balance sheet items were not made because of the short-term nature of these arrangements and the credit standing of the counterparties. Our allowance for unfunded loan commitments totaled $2.5 million at December 31, 2015 and $2.3 million at December 31, 2014. We have future commitments with third party vendors for data processing and communication charges. Data processing and communication expense was $11.7 million , $9.8 million and $9.5 million for 2015, 2014 and 2013. Included in expense was $1.3 million of one-time merger related expenses in 2015, no data processing and communication merger related expenses in 2014 and $0.8 million in one-time merger related expenses in 2013. The following table sets forth the future estimated payments related to data processing and communication charges for each of the five years following December 31, 2015: (dollars in thousands) Total 2016 $ 11,360 2017 11,743 2018 12,123 2019 12,527 2020 12,951 Total $ 60,704 Litigation In the normal course of business, we are subject to various legal and administrative proceedings and claims. While any type of litigation contains a level of uncertainty, we believe that the outcome of such proceedings or claims pending will not have a material adverse effect on our consolidated financial position or results of operations.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Income tax expense (benefit) for the years ended December 31 is comprised of: (dollars in thousands) 2015 2014 2013 Current $ 24,825 $ 15,979 $ 16,836 Deferred (427 ) 1,536 (2,358 ) Total $ 24,398 $ 17,515 $ 14,478 The provision for income taxes differs from the amount computed by applying the statutory federal income tax rate to income before income taxes. We ordinarily generate an annual effective tax rate that is less than the statutory rate of 35 percent primarily due to benefits resulting from tax-exempt interest, excludable dividend income, tax-exempt income on BOLI and tax benefits associated with LIHTC from certain partnership investments. The statutory to effective tax rate reconciliation for the years ended December 31 is as follows: 2015 2014 2013 Statutory tax rate 35.0 % 35.0 % 35.0 % Low income housing tax credits (4.4 )% (5.8 )% (6.8 )% Tax-exempt interest (4.1 )% (4.6 )% (4.5 )% Bank owned life insurance (0.8 )% (0.8 )% (1.0 )% Other 1.0 % (0.6 )% (0.4 )% Effective Tax Rate 26.7 % 23.2 % 22.3 % Significant components of our temporary differences were as follows at December 31: (dollars in thousands) 2015 2014 Deferred Tax Liabilities: Net unrealized holding gains on securities available-for-sale $ (3,563 ) $ (3,783 ) Prepaid pension (2,865 ) (3,472 ) Deferred loan income (2,847 ) (2,165 ) Purchase accounting adjustments — (631 ) Depreciation on premises and equipment (1,226 ) (1,590 ) Other (809 ) (812 ) Total Deferred Tax liabilities (11,310 ) (12,453 ) Deferred Tax Assets: Allowance for loan losses 17,740 17,567 Purchase accounting adjustments 1,298 — Other employee benefits 2,556 2,453 Low income housing partnerships 4,531 4,049 Net adjustment to funded status of pension 12,425 11,089 Impairment of securities 1,354 1,313 State net operating loss carryforwards 2,670 2,249 Other 6,155 4,668 Gross Deferred Tax Assets 48,729 43,388 Less: Valuation allowance (2,670 ) (2,249 ) Total Deferred Tax Assets 46,059 41,139 Net Deferred Tax Asset $ 34,749 $ 28,686 The Merger accounted for $12.6 million of gross deferred tax items contributing approximately $4.2 million to the increase in net deferred tax assets of $6.1 million at December 31, 2015. We establish a valuation allowance when it is more likely than not that we will not be able to realize the benefit of the deferred tax assets. Except for Pennsylvania net operating losses, or NOLs, we have determined that a valuation allowance is unnecessary for the deferred tax assets because it is more likely than not that these assets will be realized through future reversals of existing temporary differences and through future taxable income. The valuation allowance is reviewed quarterly and adjusted based on management’s assessments of realizable deferred tax assets. Gross deferred tax assets were reduced by a valuation allowance of $2.7 million in 2015 related to Pennsylvania income tax NOLs. The Pennsylvania NOL carryforwards total $26.7 million and will expire in the years 2020 - 2035 . Unrecognized Tax Benefits The following table reconciles the change in Federal and State gross unrecognized tax benefits, or UTB, for the years ended December 31: (dollars in thousands) 2015 2014 2013 Balance at beginning of year $ 284 $ 1,902 $ 978 Prior period tax positions Increase 818 55 924 Decrease — (1,673 ) — Current period tax positions — — — Reductions for statute of limitations expirations — — — Balance at End of Year $ 1,102 $ 284 $ 1,902 Amount That Would Impact the Effective Tax Rate if Recognized $ 542 $ 184 $ 148 We classify interest and penalties as an element of tax expense. We monitor changes in tax statutes and regulations to determine if significant changes will occur over the next 12 months. As of December 31, 2015, no significant changes to UTB are projected, however, tax audit examinations are possible. The UTB balance for the years ended December 31 include a cumulative amount of $0.1 million related to interest as of December 31, 2015 and 2014 and a cumulative amount of $0.3 million related to interest as of December 31, 2013 in the Consolidated Balance Sheets. We recognized an insignificant amount of interest in 2015 and 2014 and $0.2 million of interest in 2013 in the Consolidated Statements of Net Income. As of December 31, 2015, all income tax returns filed for the tax years 2012 through 2014 remain subject to examination by the IRS. Currently, our income tax return for the 2013 tax year is under examination by the IRS. We do not expect that the results of this examination will have a material effect on our financial condition or results of operations.

Tax Effects on Other Comprehens

Tax Effects on Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Tax Effects on Other Comprehensive Income (Loss)	TAX EFFECTS ON OTHER COMPREHENSIVE INCOME (LOSS) The following tables present the tax effects of the components of other comprehensive income (loss) for the years ended December 31: (dollars in thousands) Pre-Tax Amount Tax (Expense) Benefit Net of Tax Amount 2015 Net change in unrealized gains on securities available-for-sale $ (663 ) $ 232 $ (431 ) Net available-for-sale securities losses reclassified into earnings 34 (12 ) 22 Adjustment to funded status of employee benefit plans (3,551 ) 1,336 (2,215 ) Other Comprehensive Income (Loss) $ (4,180 ) $ 1,556 $ (2,624 ) 2014 Net change in unrealized losses on securities available-for-sale $ 11,825 $ (4,139 ) $ 7,686 Net available-for-sale securities gains reclassified into earnings (41 ) 15 (26 ) Adjustment to funded status of employee benefit plans (13,394 ) 4,595 (8,799 ) Other Comprehensive Income (Loss) $ (1,610 ) $ 471 $ (1,139 ) 2013 Net change in unrealized gains on securities available-for-sale $ (16,928 ) $ 5,925 $ (11,003 ) Net available-for-sale securities gains reclassified into earnings (5 ) 2 (3 ) Adjustment to funded status of employee benefit plans 18,299 (6,405 ) 11,894 Other Comprehensive Income (Loss) $ 1,366 $ (478 ) $ 888

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Benefits	EMPLOYEE BENEFITS We maintain a qualified defined benefit pension plan, or Plan, covering substantially all employees hired prior to January 1, 2008. The benefits are based on years of service and the employee’s compensation for the highest five consecutive years in the last ten years . Contributions are intended to provide for benefits attributed to employee service to date and for those benefits expected to be earned in the future. The following table summarizes the activity in the benefit obligation and Plan assets deriving the funded status, which is recorded in other liabilities in the Consolidated Balance Sheets: (dollars in thousands) 2015 2014 Change in Projected Benefit Obligation Projected benefit obligation at beginning of year $ 113,124 $ 95,969 Service cost 2,601 2,369 Interest cost 4,425 4,470 Actuarial (gain) loss (4,257 ) 16,020 Benefits paid (6,146 ) (5,704 ) Projected Benefit Obligation at End of Year $ 109,747 $ 113,124 Change in Plan Assets Fair value of plan assets at beginning of year $ 93,486 $ 89,556 Actual return on plan assets (2,755 ) 9,634 Benefits paid (6,146 ) (5,704 ) Fair Value of Plan Assets at End of Year $ 84,585 $ 93,486 Funded Status $ (25,162 ) $ (19,638 ) The following table sets forth the amounts recognized in accumulated other comprehensive income (loss) at December 31: (dollars in thousands) 2015 2014 Prior service credit $ (1,029 ) $ (1,167 ) Net actuarial loss 34,376 30,726 Total (Before Tax Effects) $ 33,347 $ 29,559 Below are the actuarial weighted average assumptions used in determining the benefit obligation: 2015 2014 Discount rate 4.25 % 4.00 % Rate of compensation increase 3.00 % 3.00 % The following table summarizes the components of net periodic pension cost and other changes in Plan assets and benefit obligations recognized in other comprehensive income (loss) for the years ended December 31: (dollars in thousands) 2015 2014 2013 Components of Net Periodic Pension Cost Service cost—benefits earned during the period $ 2,601 $ 2,369 $ 2,767 Interest cost on projected benefit obligation 4,425 4,470 3,985 Expected return on plan assets (7,180 ) (6,907 ) (6,207 ) Amortization of prior service credit (138 ) (137 ) (138 ) Recognized net actuarial loss 2,028 941 2,425 Net Periodic Pension Expense $ 1,736 $ 736 $ 2,832 Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Income (Loss) Net actuarial loss (gain) $ 5,678 $ 13,294 $ (15,499 ) Recognized net actuarial loss (2,028 ) (941 ) (2,425 ) Recognized prior service credit 138 137 138 Total (Before Tax Effects) $ 3,788 $ 12,490 $ (17,786 ) Total Recognized in Net Benefit Cost and Other Comprehensive Income (Loss) (Before Tax Effects) $ 5,524 $ 13,226 $ (14,954 ) The following table summarizes the actuarial weighted average assumptions used in determining net periodic pension cost: 2015 2014 2013 Discount rate 4.00 % 4.75 % 4.00 % Rate of compensation increase 3.00 % 3.00 % 3.00 % Expected return on assets 8.00 % 8.00 % 8.00 % The net actuarial loss included in accumulated other comprehensive income (loss) expected to be recognized in net periodic pension cost during the year ended December 31, 2016 is $2.3 million . The prior service credit expected to be recognized during the same period is $0.1 million . The accumulated benefit obligation for the Plan was $101.6 million at December 31, 2015 and $104.3 million at December 31, 2014. We consider many factors when setting the assumed rate of return on Plan assets. As a general guideline the assumed rate of return is equal to the weighted average of the expected returns for each asset category and is estimated based on historical returns as well as expected future returns. The weighted average discount rate is derived from corporate yield curves. S&T Bank’s Retirement Plan Committee determines the investment policy for the Plan. In general, the targeted asset allocation is 50 percent to 70 percent equities and 30 percent to 50 percent fixed income. A strategic allocation within each asset class is employed based on the Plan’s time horizon, risk tolerances, performance expectations and asset class preferences. Investment managers have discretion to invest in any equity or fixed-income asset class, subject to the securities guidelines of the Plan’s Investment Policy Statement. At this time, S&T Bank is not required to make a cash contribution to the Plan in 2016. No contributions were made during 2015. The following table provides information regarding estimated future benefit payments to be paid in each of the next five years and in the aggregate for the five years thereafter: (dollars in thousands) Amount 2016 $ 6,455 2017 6,250 2018 6,643 2019 6,676 2020 7,298 2021 - 2025 38,488 We also have nonqualified supplemental executive pension plans, or SERPs, for certain key employees. The SERPs are unfunded. The projected benefit obligations related to the SERPs were $4.0 million and $3.5 million at December 31, 2015 and 2014. These amounts also represent the net amount recognized in the statement of financial position for the SERPs. Net periodic benefit costs for the SERPs were $0.6 million , $0.4 million and $0.4 million for each of the years ended December 31, 2015, 2014 and 2013. Additionally, $2.1 million before tax was reflected in accumulated other comprehensive income (loss) at both December 31, 2015 and 2014, in relation to the SERPs. The actuarial assumptions used for the SERPs are the same as those used for the Plan. On January 25, 2016, the Board of Directors approved an amendment to freeze benefit accruals under the qualified and nonqualified defined benefit pension plans effective March 31, 2016. This change will result in no additional benefits being earned by participants in those plans based on service or pay after March 31, 2016. The Plan was previously closed to new participants effective December 31, 2007. We maintain a Thrift Plan, a qualified defined contribution plan, in which substantially all employees are eligible to participate. We make matching contributions to the Thrift Plan up to 3.5 percent of participants’ eligible compensation and may make additional profit-sharing contributions as provided by the Thrift Plan. Expense related to these contributions amounted to $1.5 million in 2015, $1.3 million in 2014 and $1.4 million in 2013. Fair Value Measurements The following tables present our Plan assets measured at fair value on a recurring basis by fair value hierarchy level at December 31, 2015 and 2014. There were no transfers between Level 1 and Level 2 for items of a recurring basis during the periods presented. There were no purchases or transfers of Level 3 plan assets in 2015. December 31, 2015 Fair Value Asset Classes (1) (dollars in thousands) Level 1 Level 2 Level 3 Total Cash and cash equivalents (2) $ — $ 3,371 $ — $ 3,371 Fixed income (3) 27,054 — — 27,054 Equities: Equity index mutual funds—international (4) 3,421 — — 3,421 Domestic individual equities (5) 50,739 — — 50,739 Total Assets at Fair Value $ 81,214 $ 3,371 $ — $ 84,585 (1) Refer to Note 1 Summary of Significant Accounting Policies, Fair Value Measurements for a description of levels within the fair value hierarchy. (2) This asset class includes FDIC insured money market instruments. (3) This asset class includes a variety of fixed income mutual funds which primarily invest in investment grade rated securities. Investment managers have discretion to invest in fixed income related securities including futures, options and other derivatives. Investments may be made in currencies other than the U.S. dollar. (4) The sole investment within this asset class is the Harbor International Institutional Fund. (5) This asset class includes individual domestic equities invested in an active all-cap strategy. It may also include convertible bonds. December 31, 2014 Fair Value Asset Classes (1) (dollars in thousands) Level 1 Level 2 Level 3 Total Cash and cash equivalents (2) $ — $ 5,073 $ — $ 5,073 Fixed income (3) 26,726 — — 26,726 Equities: Equity index mutual funds—international (4) 3,728 — — 3,728 Domestic individual equities (5) 57,085 — — 57,085 International individual equities (6) 874 — — 874 Total Assets at Fair Value $ 88,413 $ 5,073 $ — $ 93,486 (1) Refer to Note 1 Summary of Significant Accounting Policies, Fair Value Measurements for a description of levels within the fair value hierarchy. (2) This asset class includes FDIC insured money market instruments. (3) This asset class includes a variety of fixed income mutual funds which primarily invest in investment grade rated securities. Investment managers have discretion to invest in fixed income related securities including futures, options and other derivatives. Investments may be made in currencies other than the U.S. dollar. (4) The sole investment within this asset class is MSCI EAFE Index iShares. (5) This asset class includes individual domestic equities invested in an active all-cap strategy. It may also include convertible bonds. (6) This asset class includes American Depository Receipts.

Incentive and Restricted Stock

Incentive and Restricted Stock Plan and Dividend Reinvestment Plan	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Incentive and Restricted Stock Plan and Dividend Reinvestment Plan	INCENTIVE AND RESTRICTED STOCK PLAN AND DIVIDEND REINVESTMENT PLAN We adopted an Incentive Stock Plan in 2003 that provides for granting incentive stock options, nonstatutory stock options, restricted stock and appreciation rights. The 2003 Stock Plan had a maximum of 1,500,000 shares of our common stock that expired ten years from the date of board approval. No further awards will be granted under the 2003 Stock Plan and there are no awards outstanding under the plan as of December 31, 2015. We adopted an Incentive Stock Plan in 2014 that provides for cash performance awards and for granting incentive stock options, nonstatutory stock options, restricted stock, restricted stock units and appreciation rights. The 2014 Incentive Plan has a maximum of 750,000 shares of our common stock and expires ten years from the date of board approval. With respect to stock compensation provisions, the 2014 Incentive Plan is similar to the 2003 Stock Plan, which the 2014 Stock Plan replaced. Stock Options As of December 31, 2015, no nonstatutory stock options are outstanding under the 2003 Stock Plan or the 2014 Stock Plan. Nonstatutory stock options granted in 2005 are fully vested and had a ten year life. These stock options were fully expensed in 2010. The fair value of nonstatutory stock option awards under the 2003 Stock Plan were estimated on the date of grant using the Black-Scholes valuation model, which is dependent upon certain assumptions. We use the simplified method in developing the estimated life of the option, whereby the expected life is presumed to be the midpoint between the vesting date and the end of the contractual term. There have been no nonstatutory stock options granted since 2006. The following table summarizes activity for nonstatutory stock options for the years ended December 31: 2015 2014 2013 Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at beginning of year 155,500 $ 37.86 428,900 $ 37.36 675,500 $ 35.18 Granted — — — — — — Exercised — — — — — — Forfeited — — (273,400 ) 37.08 (246,600 ) 31.39 Expired (155,500 ) 37.86 — — — — Outstanding at End of Year — — 0.0 years 155,500 $ 37.86 1.0 year 428,900 $ 37.36 1.4 years Exercisable at End of Year — — 0.0 years 155,500 $ 37.86 1.0 year 428,900 $ 37.36 1.4 years The aggregate intrinsic value of options outstanding and exercisable was zero as of December 31, 2014 and 2013. The aggregate intrinsic value represents the total pretax intrinsic value (the difference between our closing stock price on the last trading day of the fourth quarter and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised the options on December 31, 2014 and 2013. Restricted Stock We periodically issue restricted stock to employees and directors, pursuant to our Stock Plans. As of December 31, 2015, 259,673 restricted shares have been granted under the 2003 Stock Plan and 168,296 restricted shares have been granted under the 2014 Stock Plan. During 2015, 2014, and 2013, we granted 16,142 , 13,824 and 18,942 restricted shares of common stock, to outside directors. The 2015 and 2014 grants were issued under the 2014 Stock Plan and the 2013 grants were issued under the 2003 Stock Plan. The grants are part of the compensation arrangement approved by the Compensation and Benefits Committee whereby the directors receive compensation in both the form of cash and restricted shares of common stock. These shares fully vest one year after the date of grant. The fair value is determined by the closing price of the stock on the date of grant. During 2015, 2014, and 2013, we granted 71,699 , 66,631 and 3,247 restricted shares of common stock to senior management under our Long Term Incentive Plan, or LTIP. The restricted shares granted under the LTIP for 2015 and 2014 of 71,699 and 66,631 shares, consisted of both time and performance-based awards. The 2015 and 2014 grants were issued under the 2014 Stock Plan and the 2013 grants were issued under the 2003 Stock Plan. The awards to senior management were granted in accordance with performance levels set by the Compensation and Benefits Committee. Vesting for the time-based awards is 50 percent after two years and the remaining 50 percent at the end of the third year. The performance-based awards vest at the end of the three-year period. During the vesting period, the recipient receives dividends and has the right to vote the unvested shares granted, except for the 2015 and 2014 LTIP performance-based awards. If the recipient leaves S&T before the end of the vesting period, shares will be forfeited except in the case of retirement, disability or death where accelerated vesting provisions are defined within the awards agreement. During 2013, additional restricted shares were granted on two occasions with different vesting periods. The restricted stock grants for 2013 of 3,247 shares vested fully on the second anniversary of the grant date. Compensation expense for time-based restricted stock is recognized ratably over the period of service, generally the entire vesting period, based on fair value on the date of grant. Compensation expense for performance-based restricted stock is recognized ratably over the remaining vesting period once the likelihood of meeting the performance measure is probable. The average of the high and low prices of the stock on the grant date is used for senior management. During 2015, 2014 and 2013, we recognized compensation expense of $1.7 million , $0.9 million and $0.6 million and realized a tax benefit of $0.6 million , $0.3 million and $0.2 million related to restricted stock grants. The following table provides information about restricted stock granted under the 2003 Stock Plan for the years ended December 31: Restricted Stock Weighted Average Grant Date Fair Value Non-vested at December 31, 2013 79,415 $ 21.50 Granted — — Vested 41,740 20.70 Forfeited 14,530 20.97 Non-vested at December 31, 2014 23,145 $ 23.28 Granted — — Vested 15,433 22.34 Forfeited 7,712 22.34 Non-vested at December 31, 2015 — $ — The following table provides information about restricted stock granted under the 2014 Stock Plan for the years ended December 31: Restricted Stock Weighted Average Grant Date Fair Value Non-vested at December 31, 2013 — $ — Granted 80,455 23.24 Vested 158 23.19 Forfeited 473 23.19 Non-vested at December 31, 2014 79,824 $ 23.24 Granted 87,841 28.71 Vested 14,126 23.57 Forfeited 3,183 26.15 Non-vested at December 31, 2015 150,356 $ 26.34 As of December 31, 2015, there was $2.3 million of total unrecognized compensation cost related to restricted stock that will be recognized as compensation expense over a weighted average period of 1.66 years. Dividend Reinvestment Plan We also sponsor a Dividend Reinvestment and Stock Purchase Plan, or Dividend Plan, where shareholders may purchase shares of S&T common stock at the average fair value with reinvested dividends and voluntary cash contributions. The plan administrator and transfer agent may purchase shares directly from us from shares held in treasury or purchase shares in the open market to fulfill the Dividend Plan’s needs.

Parent Company Condensed Financ

Parent Company Condensed Financial Information	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Condensed Financial Information	PARENT COMPANY CONDENSED FINANCIAL INFORMATION The following condensed financial statements summarize the financial position of S&T Bancorp, Inc. as of December 31, 2015 and 2014 and the results of its operations and cash flows for each of the three years ended December 31, 2015, 2014 and 2013. BALANCE SHEETS December 31, (dollars in thousands) 2015 2014 ASSETS Cash $ 12,595 $ 38,028 Investments in: Bank subsidiary 777,795 565,927 Nonbank subsidiaries 20,624 20,569 Other assets 2,530 5,567 Total Assets $ 813,544 $ 630,091 LIABILITIES Long-term debt $ 20,619 $ 20,619 Other liabilities 688 1,083 Total Liabilities 21,307 21,702 Total Shareholders’ Equity 792,237 608,389 Total Liabilities and Shareholders’ Equity $ 813,544 $ 630,091 STATEMENTS OF NET INCOME Years ended December 31, (dollars in thousands) 2015 2014 2013 Dividends from subsidiaries $ 75,413 $ 46,414 $ 24,087 Investment income 19 19 15 Interest expense on long-term debt 773 759 769 Other expenses 2,138 2,014 2,579 Income before Equity in Undistributed Net Income of Subsidiaries 72,521 43,660 20,754 Equity in undistributed net income (distribution in excess of net income) of: Bank subsidiary (5,064 ) 13,351 29,926 Nonbank subsidiaries (376 ) 899 (141 ) Net Income $ 67,081 $ 57,910 $ 50,539 STATEMENTS OF CASH FLOWS Years ended December 31, (dollars in thousands) 2015 2014 2013 OPERATING ACTIVITIES Net Income $ 67,081 $ 57,910 $ 50,539 Equity in undistributed (earnings) losses of subsidiaries 5,440 (14,250 ) (29,785 ) Tax benefit from stock-based compensation (53 ) (16 ) (96 ) Other 3,059 (106 ) 121 Net Cash Provided by Operating Activities 75,527 43,538 20,779 INVESTING ACTIVITIES Net investments in subsidiaries (38,404 ) — — Acquisitions (29,510 ) — — Net Cash Used in Investing Activities (67,914 ) — — FINANCING ACTIVITIES Repayment of junior subordinated debt (8,500 ) — — (Purchase) Sale of treasury shares, net (112 ) (163 ) (88 ) Cash dividends paid to common shareholders (24,487 ) (20,215 ) (18,137 ) Tax benefit from stock-based compensation 53 16 96 Net Cash Used in Financing Activities (33,046 ) (20,362 ) (18,129 ) Net increase (decrease) in cash (25,433 ) 23,176 2,650 Cash at beginning of year 38,028 14,852 12,202 Cash at End of Year $ 12,595 $ 38,028 $ 14,852

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Regulatory Matters	REGULATORY MATTERS We are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet the minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on our consolidated financial statements. Under capital guidelines and the regulatory framework for prompt corrective action, we must meet specific capital guidelines that involve quantitative measures of our assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. Our capital amounts and classification are also subject to qualitative judgments by the regulators about risk weightings and other factors. The most recent notifications from the Federal Reserve and the FDIC categorized S&T and S&T Bank as well capitalized under the regulatory framework for corrective action. There have been no conditions or events that we believe have changed S&T or S&T Bank’s status during 2015 and 2014. Tier 1 capital consists principally of shareholders’ equity, including preferred stock; excluding items recorded in accumulated other comprehensive income (loss), less goodwill and other intangibles. For regulatory purposes, trust preferred securities totaling $20.0 million , issued by an unconsolidated trust subsidiary of S&T underlying junior subordinated debt, are included in Tier 1 capital for S&T. Total capital consists of Tier 1 capital plus junior subordinated debt and the ALL subject to limitation. We currently have $25.0 million in junior subordinated debt which is included in Tier 2 capital for S&T in accordance with current regulatory reporting requirements. Quantitative measures established by regulation to ensure capital adequacy require us to maintain minimum amounts and ratios of Total, Tier 1 and Common Equity Tier 1 capital to risk-weighted assets and Tier 1 capital to average assets. As of December 31, 2015 and 2014, we met all capital adequacy requirements to which we are subject. The following table summarizes risk-based capital amounts and ratios for S&T and S&T Bank: Actual Minimum Regulatory Capital Requirements To be Well Capitalized Under Prompt Corrective Action Provisions (dollars in thousands) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2015 Leverage Ratio S&T $ 535,234 8.96 % $ 238,841 4.00 % $ 298,551 5.00 % S&T Bank 502,114 8.43 % 238,121 4.00 % 297,651 5.00 % Common Equity Tier 1 (to Risk-Weighted Assets) S&T 515,234 9.77 % 237,315 4.50 % 342,788 6.50 % S&T Bank 502,114 9.55 % 236,482 4.50 % 341,584 6.50 % Tier 1 Capital (to Risk-Weighted Assets) S&T 535,234 10.15 % 316,419 6.00 % 421,892 8.00 % S&T Bank 502,114 9.55 % 315,309 6.00 % 420,412 8.00 % Total Capital (to Risk-Weighted Assets) S&T 611,859 11.60 % 421,892 8.00 % 527,366 10.00 % S&T Bank 577,824 11.00 % 420,412 8.00 % 525,515 10.00 % As of December 31, 2014 Leverage Ratio (1) S&T $ 465,114 9.80 % $ 189,895 4.00 % $ 237,369 5.00 % S&T Bank 403,593 8.53 % 189,182 4.00 % 236,477 5.00 % Common Equity Tier 1 (to Risk-Weighted Assets) S&T 445,114 11.81 % 169,621 4.50 % 245,008 6.50 % S&T Bank 403,593 10.76 % 168,804 4.50 % 243,827 6.50 % Tier 1 Capital (to Risk-Weighted Assets) S&T 465,114 12.34 % 150,774 4.00 % 226,161 6.00 % S&T Bank 403,593 10.76 % 150,048 4.00 % 225,071 6.00 % Total Capital (to Risk-Weighted Assets) S&T 537,935 14.27 % 301,548 8.00 % 376,936 10.00 % S&T Bank 475,538 12.68 % 300,095 8.00 % 375,119 10.00 %

Segments

Segments	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segments	SEGMENTS We operate three reportable operating segments: Community Banking, Insurance and Wealth Management. • Our Community Banking segment offers services which include accepting time and demand deposits and originating commercial and consumer loans. • Our Insurance segment includes a full-service insurance agency offering commercial property and casualty insurance, group life and health coverage, employee benefit solutions and personal insurance lines. • Our Wealth Management segment offers discount brokerage services, services as executor and trustee under wills and deeds, guardian and custodian of employee benefits and other trust and brokerage services, as well as a registered investment advisor that manages private investment accounts for individuals and institutions. The following represents total assets by reportable operating segment as of December 31: (dollars in thousands) 2015 2014 Community Banking $ 6,305,046 $ 4,954,728 Insurance 9,619 7,468 Wealth Management 3,689 2,490 Total Assets $ 6,318,354 $ 4,964,686 The following tables provide financial information for our three segments. The financial results of the business segments include allocations for shared services based on an internal analysis that supports line of business and branch performance measurement. Shared services include expenses such as employee benefits, occupancy expense, computer support and other corporate overhead. Even with these allocations, the financial results are not necessarily indicative of the business segments’ financial condition and results of operations as if they existed as independent entities. The information provided under the caption “Eliminations” represents operations not considered to be reportable segments and/or general operating expenses and eliminations and adjustments, which are necessary for purposes of reconciling to the Consolidated Financial Statements. For the Year Ended December 31, 2015 (dollars in thousands) Community Banking Insurance Wealth Management Eliminations Consolidated Interest income $ 203,439 $ 2 $ 508 $ (401 ) $ 203,548 Interest expense 16,678 — — (681 ) 15,997 Net interest income 186,761 2 508 280 187,551 Provision for loan losses 10,388 — — — 10,388 Noninterest income 34,106 5,035 11,412 480 51,033 Noninterest expense 115,998 4,365 9,037 760 130,160 Depreciation expense 4,664 50 25 — 4,739 Amortization of intangible assets 1,738 50 30 — 1,818 Provision for income taxes 23,209 200 989 — 24,398 Net Income $ 64,870 $ 372 $ 1,839 $ — $ 67,081 For the Year Ended December 31, 2014 (dollars in thousands) Community Banking Insurance Wealth Management Eliminations Consolidated Interest income $ 160,403 $ 2 $ 518 $ (400 ) $ 160,523 Interest expense 13,989 — — (1,508 ) 12,481 Net interest income 146,414 2 518 1,108 148,042 Provision for loan losses 1,715 — — — 1,715 Noninterest income 29,443 5,279 11,297 319 46,338 Noninterest expense 97,733 4,313 9,173 1,427 112,646 Depreciation expense 3,387 51 27 — 3,465 Amortization of intangible assets 1,039 51 39 — 1,129 Provision for income taxes 16,311 303 901 — 17,515 Net Income $ 55,672 $ 563 $ 1,675 $ — $ 57,910 For the Year Ended December 31, 2013 (dollars in thousands) Community Banking Insurance Wealth Management Eliminations Consolidated Interest income $ 153,450 $ 2 $ 517 $ (213 ) $ 153,756 Interest expense 16,508 — — (1,945 ) 14,563 Net interest income 136,942 2 517 1,732 139,193 Provision for loan losses 8,311 — — — 8,311 Noninterest income 34,649 5,483 10,662 733 51,527 Noninterest expense 94,769 5,210 9,850 2,465 112,294 Depreciation expense 3,430 47 30 — 3,507 Amortization of intangible assets 1,492 51 48 — 1,591 Provision (benefit) for income taxes 14,180 (47 ) 345 — 14,478 Net Income $ 49,409 $ 224 $ 906 $ — $ 50,539

Selected Financial Data

Selected Financial Data	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Selected Financial Data	SELECTED FINANCIAL DATA The following table presents selected financial data for the most recent eight quarters. 2015 2014 (dollars in thousands, except per share data) (unaudited) Fourth Quarter Third Quarter Second Quarter First Quarter Fourth Quarter Third Quarter Second Quarter First Quarter SUMMARY OF OPERATIONS Interest income $ 53,353 $ 53,669 $ 52,611 $ 43,916 $ 41,381 $ 40,605 $ 39,872 $ 38,665 Interest expense 4,468 4,073 3,800 3,657 3,315 3,076 3,017 3,074 Provision for loan losses 3,915 3,206 2,059 1,207 1,106 1,454 (1,134 ) 289 Net Interest Income After Provision For Loan Losses 44,970 46,390 46,752 39,052 36,960 36,075 37,989 35,302 Security (losses) gains, net — — (34 ) — — — 40 1 Noninterest income 13,084 12,481 13,417 12,084 11,220 11,931 11,731 11,415 Noninterest expense 33,817 33,829 35,449 33,621 29,720 28,440 30,165 28,914 Income Before Taxes 24,237 25,042 24,686 17,515 18,460 19,566 19,595 17,804 Provision for income taxes 6,814 6,407 6,498 4,680 3,963 4,906 4,875 3,771 Net Income Available to Common Shareholders $ 17,423 $ 18,635 $ 18,188 $ 12,835 $ 14,497 $ 14,660 $ 14,720 $ 14,033 Per Share Data Common earnings per share—diluted $ 0.50 $ 0.54 $ 0.52 $ 0.41 $ 0.49 $ 0.49 $ 0.49 $ 0.47 Dividends declared per common share 0.19 0.18 0.18 0.18 0.18 0.17 0.17 0.16 Common book value 22.76 22.63 22.15 21.91 20.42 20.33 20.04 19.64

Sale of Merchant Card Servicing

Sale of Merchant Card Servicing Business	12 Months Ended
	Dec. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Sale of Merchant Card Servicing Business	SALE OF MERCHANT CARD SERVICING BUSINESS We sold our existing merchant card servicing business for $4.8 million during the first quarter of 2013. Consequently, we terminated an agreement with our existing merchant processor and incurred a termination fee of $1.7 million . As a result of this transaction, we recognized a gain of $3.1 million in the first quarter of 2013. In conjunction with the sale of the merchant card servicing business, we entered into a marketing and sales alliance agreement with the purchaser for an initial term of ten years . The agreement provides that we will actively market and refer our customers to the purchaser and in return will receive a share of the future revenue. Future revenue is dependent on the number of referrals, number of new merchant accounts and volume of activity.

Summary of Significant Accoun36

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations S&T Bancorp, Inc., or S&T, was incorporated on March 17, 1983 under the laws of the Commonwealth of Pennsylvania as a bank holding company and has three wholly owned subsidiaries, S&T Bank, 9th Street Holdings, Inc. and STBA Capital Trust I. We own a 50 percent interest in Commonwealth Trust Credit Life Insurance Company, or CTCLIC. We are presently engaged in nonbanking activities through the following five entities: 9th Street Holdings, Inc.; S&T Bancholdings, Inc.; CTCLIC; S&T Insurance Group, LLC and Stewart Capital Advisors, LLC. 9th Street Holdings, Inc. and S&T Bancholdings, Inc. are investment holding companies. CTCLIC, which is a joint venture with another financial institution, acts as a reinsurer of credit life, accident and health insurance policies sold by S&T Bank and the other institution. S&T Insurance Group, LLC, through its subsidiaries, offers a variety of insurance products. Stewart Capital Advisors, LLC is a registered investment advisor that manages private investment accounts for individuals and institutions and advises the Stewart Capital Mid Cap Fund. On October 29, 2014, S&T and Integrity Bancshares, Inc., or Integrity, based in Camp Hill, Pennsylvania, entered into an agreement to acquire Integrity Bancshares, Inc. and the transaction was completed on March 4, 2015. Integrity Bank was subsequently merged into S&T Bank on May 8, 2015. S&T Bank is operating under the name "Integrity Bank - A Division of S&T Bank" in south-central Pennsylvania.
Accounting Policies	Accounting Policies Our financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP. In preparing the financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the dates of the balance sheets and revenues and expenses for the periods then ended. Actual results could differ from those estimates. Our significant accounting policies are described below.
Principles of Consolidation	Principles of Consolidation The Consolidated Financial Statements include the accounts of S&T and its wholly owned subsidiaries. All significant intercompany transactions have been eliminated in consolidation. Investments of 20 percent to 50 percent of the outstanding common stock of investees are accounted for using the equity method of accounting.
Reclassification	Reclassification Certain amounts in prior years’ financial statements and footnotes have been reclassified to conform to the current year’s presentation. The reclassifications had no significant effect on our results of operations or financial condition.
Business Combinations	Business Combinations We account for business combinations using the acquisition method of accounting. Under this method of accounting, the acquired company’s net assets are recorded at fair value at the date of acquisition, and the results of operations of the acquired company are combined with our results from that date forward. Acquisition costs are expensed when incurred. The difference between the purchase price and the fair value of the net assets acquired (including identified intangibles) is recorded as goodwill.
Fair Value Measurements	Fair Value Measurements We use fair value measurements when recording and disclosing certain financial assets and liabilities. Securities available-for-sale, trading assets and derivative financial instruments are recorded at fair value on a recurring basis. Additionally, from time to time, we may be required to record other assets at fair value on a nonrecurring basis, such as loans held for sale, impaired loans, other real estate owned, or OREO, and other repossessed assets, mortgage servicing rights, or MSRs, and certain other assets. Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants at the measurement date. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets or liabilities; it is not a forced transaction. In determining fair value, we use various valuation approaches, including market, income and cost approaches. The fair value standard establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing an asset or liability, which are developed, based on market data we have obtained from independent sources. Unobservable inputs reflect our estimates of assumptions that market participants would use in pricing an asset or liability, which are developed based on the best information available in the circumstances. The fair value hierarchy gives the highest priority to unadjusted quoted market prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). The fair value hierarchy is broken down into three levels based on the reliability of inputs as follows: Level 1: valuation is based upon unadjusted quoted market prices for identical instruments traded in active markets. Level 2: valuation is based upon quoted market prices for similar instruments traded in active markets, quoted market prices for identical or similar instruments traded in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by market data. Level 3: valuation is derived from other valuation methodologies, including discounted cash flow models and similar techniques that use significant assumptions not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in determining fair value. A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Our policy is to recognize transfers between any of the fair value hierarchy levels at the end of the reporting period in which the transfer occurred. The following are descriptions of the valuation methodologies that we use for financial instruments recorded at fair value on either a recurring or nonrecurring basis. Recurring Basis Securities Available-for-Sale Securities available-for-sale include both debt and equity securities. We obtain fair values for debt securities from a third-party pricing service which utilizes several sources for valuing fixed-income securities. We validate prices received from our pricing service through comparison to a secondary pricing service and broker quotes. We review the methodologies of the pricing service which provides us with a sufficient understanding of the valuation models, assumptions, inputs and pricing to reasonably measure the fair value of our debt securities. The market evaluation sources for debt securities include observable inputs rather than significant unobservable inputs and are classified as Level 2. The service provider utilizes pricing models that vary by asset class and include available trade, bid and other market information. Generally, the methodologies include broker quotes, proprietary models, and vast descriptive terms and conditions databases, as well as extensive quality control programs. Marketable equity securities that have an active, quotable market are classified as Level 1. Marketable equity securities that are quotable, but are thinly traded or inactive, are classified as Level 2. Marketable equity securities that are not readily traded and do not have a quotable market are classified as Level 3. Trading Assets We use quoted market prices to determine the fair value of our trading assets. Our trading assets are held in a Rabbi Trust under a deferred compensation plan and are invested in readily quoted mutual funds. Accordingly, these assets are classified as Level 1. Derivative Financial Instruments We use derivative instruments, including interest rate swaps for commercial loans with our customers, interest rate lock commitments and the sale of mortgage loans in the secondary market. We calculate the fair value for derivatives using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. Each valuation considers the contractual terms of the derivative, including the period to maturity, and uses observable market based inputs, such as interest rate curves and implied volatilities. Accordingly, derivatives are classified as Level 2. We incorporate credit valuation adjustments into the valuation models to appropriately reflect both our own nonperformance risk and the respective counterparties’ nonperformance risk in calculating fair value measurements. In adjusting the fair value of our derivative contracts for the effect of nonperformance risk, we have considered the impact of netting and any applicable credit enhancements and collateral postings. Nonrecurring Basis Loans Held for Sale Loans held for sale consist of 1-4 family residential loans originated for sale in the secondary market and, from time to time, certain loans transferred from the loan portfolio to loans held for sale, all of which are carried at the lower of cost or fair value. The fair value of 1-4 family residential loans is based on the principal or most advantageous market currently offered for similar loans using observable market data. The fair value of the loans transferred from the loan portfolio is based on the amounts offered for these loans in currently pending sales transactions. Loans held for sale carried at fair value are classified as Level 3. Impaired Loans Impaired loans are carried at the lower of carrying value or fair value. Fair value is determined as the recorded investment balance less any specific reserve. We establish specific reserves based on the following three impairment methods: 1) the present value of expected future cash flows discounted at the loan’s original effective interest rate, 2) the loan’s observable market price or 3) the fair value of the collateral less estimated selling costs when the loan is collateral dependent and we expect to liquidate the collateral. However, if repayment is expected to come from the operation of the collateral, rather than liquidation, then we do not consider estimated selling costs in determining the fair value of the collateral. Collateral values are generally based upon appraisals by approved, independent state certified appraisers. Appraisals may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or our knowledge of the borrower and the borrower’s business. Impaired loans carried at fair value are classified as Level 3. OREO and Other Repossessed Assets OREO and other repossessed assets obtained in partial or total satisfaction of a loan are recorded at the lower of recorded investment in the loan or fair value less cost to sell. Subsequent to foreclosure, these assets are carried at the lower of the amount recorded at acquisition date or fair value less cost to sell. Accordingly, it may be necessary to record nonrecurring fair value adjustments. Fair value, when recorded, is generally based upon appraisals by approved, independent state certified appraisers. Like impaired loans, appraisals on OREO may be discounted based on our historical knowledge, changes in market conditions from the time of appraisal or other information available to us. OREO and other repossessed assets carried at fair value are classified as Level 3. Mortgage Servicing Rights The fair value of MSRs is determined by calculating the present value of estimated future net servicing cash flows, considering expected mortgage loan prepayment rates, discount rates, servicing costs and other economic factors, which are determined based on current market conditions. The expected rate of mortgage loan prepayments is the most significant factor driving the value of MSRs. MSRs are considered impaired if the carrying value exceeds fair value. The valuation model includes significant unobservable inputs; therefore, MSRs are classified as Level 3. Other Assets We measure certain other assets at fair value on a nonrecurring basis. Fair value is based on the application of lower of cost or fair value accounting, or write-downs of individual assets. Valuation methodologies used to measure fair value are consistent with overall principles of fair value accounting and consistent with those described above. Financial Instruments In addition to financial instruments recorded at fair value in our financial statements, fair value accounting guidance requires disclosure of the fair value of all of an entity’s assets and liabilities that are considered financial instruments. The majority of our assets and liabilities are considered financial instruments. Many of these instruments lack an available trading market as characterized by a willing buyer and willing seller engaged in an exchange transaction. Also, it is our general practice and intent to hold our financial instruments to maturity and to not engage in trading or sales activities with respect to such financial instruments. For fair value disclosure purposes, we substantially utilize the fair value measurement criteria as required and explained above. In cases where quoted fair values are not available, we use present value methods to determine the fair value of our financial instruments. Cash and Cash Equivalents The carrying amounts reported in the Consolidated Balance Sheets for cash and due from banks, including interest-bearing deposits, approximate fair value. Loans The fair value of variable rate performing loans that may reprice frequently at short-term market rates is based on carrying values adjusted for credit risk. The fair value of variable rate performing loans that reprice at intervals of one year or longer, such as adjustable rate mortgage products, is estimated using discounted cash flow analyses that utilize interest rates currently being offered for similar loans and adjusted for credit risk. The fair value of fixed rate performing loans is estimated using a discounted cash flow analysis that utilizes interest rates currently being offered for similar loans and adjusted for credit risk. The fair value of impaired nonperforming loans is based on their carrying values less any specific reserve. The carrying amount of accrued interest approximates fair value. Bank Owned Life Insurance Fair value approximates net cash surrender value of bank owned life insurance, or BOLI. Federal Home Loan Bank, or FHLB, and Other Restricted Stock It is not practical to determine the fair value of our FHLB and other restricted stock due to the restrictions placed on the transferability of these stocks; it is presented at carrying value. Deposits The fair values disclosed for deposits without defined maturities (e.g., noninterest and interest-bearing demand, money market and savings accounts) are by definition equal to the amounts payable on demand. The carrying amounts for variable rate, fixed-term time deposits approximate their fair values. Estimated fair values for fixed rate and other time deposits are based on discounted cash flow analysis using interest rates currently offered for time deposits with similar terms. The carrying amount of accrued interest approximates fair value. Short-Term Borrowings The carrying amounts of securities sold under repurchase agreements, or REPOs, and other short-term borrowings approximate their fair values. Long-Term Borrowings The fair values disclosed for fixed rate long-term borrowings are determined by discounting their contractual cash flows using current interest rates for long-term borrowings of similar remaining maturities. The carrying amounts of variable rate long-term borrowings approximate their fair values. Junior Subordinated Debt Securities The variable rate junior subordinated debt securities reprice quarterly; therefore, the carrying values approximate their fair values. Loan Commitments and Standby Letters of Credit Off-balance sheet financial instruments consist of commitments to extend credit and letters of credit. Except for interest rate lock commitments, estimates of the fair value of these off-balance sheet items are not made because of the short-term nature of these arrangements and the credit standing of the counterparties. Other Estimates of fair value are not made for items that are not defined as financial instruments, including such items as our core deposit intangibles and the value of our trust operations.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider cash and due from banks, interest-bearing deposits with banks and federal funds sold as cash and cash equivalents.
Securities	Securities We determine the appropriate classification of securities at the time of purchase. All securities, including both debt and equity securities, are classified as available-for-sale. These are securities that we intend to hold for an indefinite period of time, but that may be sold in response to changes in interest rates, prepayment risk, liquidity needs or other factors. Such securities are carried at fair value with net unrealized gains and losses deemed to be temporary, reported as a component of other comprehensive income (loss), net of tax. Realized gains and losses on the sale of available-for-sale securities and other-than-temporary impairment, or OTTI, charges are recorded within noninterest income in the Consolidated Statements of Net Income. Realized gains and losses on the sale of securities are determined using the specific-identification method. Bond premiums are amortized to the call date and bond discounts are accreted to the maturity date, both on a level yield basis. An investment security is considered impaired if its fair value is less than its cost or amortized cost basis. We perform a quarterly review of our securities to identify those that may indicate an OTTI. Our policy for OTTI within the marketable equity securities portfolio generally requires an impairment charge when the security is in a loss position for 12 consecutive months, unless facts and circumstances would suggest the need for an OTTI prior to that time. Our policy for OTTI within the debt securities portfolio is based upon a number of factors, including but not limited to, the length of time and extent to which the estimated fair value has been less than cost, the financial condition of the underlying issuer, the ability of the issuer to meet contractual obligations, the best estimate of the impairment charge representing credit losses, the likelihood of the security’s ability to recover any decline in its estimated fair value and whether management intends to sell the security or if it is more likely than not that management will be required to sell the investment security prior to the security’s recovery of any decline in its estimated fair value. If the impairment is considered other-than-temporary based on management’s review, the impairment must be separated into credit and non-credit components. The credit component is recognized in the Consolidated Statements of Net Income and the non-credit component is recognized in other comprehensive income (loss), net of applicable taxes.
Loans Held for Sale	Loans Held for Sale Loans held for sale consist of 1-4 family residential loans originated for sale in the secondary market and from time to time, certain loans transferred from the loan portfolio to loans held for sale, all of which are carried at the lower of cost or fair value. If a loan is transferred from the loan portfolio to the held for sale category, any write-down in the carrying amount of the loan at the date of transfer is recorded as a charge-off against the allowance for loan losses, or ALL. Subsequent declines in fair value are recognized as a charge to noninterest income. When a loan is placed in the held for sale category, we stop amortizing the related deferred fees and costs. The remaining unamortized fees and costs are recognized as part of the cost basis of the loan at the time it is sold. Gains and losses on sales of loans held for sale are included in other noninterest income in the Consolidated Statements of Net Income.
Loans	Loans Loans are reported at the principal amount outstanding net of unearned income, unamortized premiums or discounts and deferred origination fees and costs. We defer certain nonrefundable loan origination and commitment fees. Accretion of discounts and amortization of premiums on loans are included in interest income in the Consolidated Statements of Net Income. Loan origination fees and direct loan origination costs are deferred and amortized as an adjustment of loan yield over the respective lives of the loans without consideration of anticipated prepayments. If a loan is paid off, the remaining unaccreted or unamortized net origination fees and costs are immediately recognized into income or expense. Interest is accrued and interest income is recognized on loans as earned. Acquired loans are recorded at fair value on the date of acquisition with no carryover of the related ALL. Determining the fair value of the acquired loans involves estimating the principal and interest cash flows expected to be collected on the loans and discounting those cash flows at a market rate of interest. In estimating the fair value of our acquired loans, we consider a number of factors including the loan term, internal risk rating, delinquency status, prepayment rates, recovery periods, estimated value of the underlying collateral and the current interest rate environment. Closed-end installment loans, amortizing loans secured by real estate and any other loans with payments scheduled monthly are reported past due when the borrower is in arrears two or more monthly payments. Other multi-payment obligations with payments scheduled other than monthly are reported past due when one scheduled payment is due and unpaid for 30 days or more. Generally, consumer loans are charged off against the ALL upon the loan reaching 90 days past due. Commercial loans are charged off as management becomes aware of facts and circumstances that raise doubt as to the collectability of all or a portion of the principal and when we believe a confirmed loss exists.
Nonaccrual or Nonperforming Loans	Nonaccrual or Nonperforming Loans We stop accruing interest on a loan when the borrower’s payment is 90 days past due. Loans are also placed on nonaccrual status when payment is not past due, but we have doubt about the borrower’s ability to comply with contractual repayment terms. When the interest accrual is discontinued, all unpaid accrued interest is reversed against interest income. Interest income is recognized on nonaccrual loans on a cash basis if recovery of the remaining principal is reasonably assured. As a general rule, a nonaccrual loan may be restored to accrual status when its principal and interest is paid current and the bank expects repayment of the remaining contractual principal and interest, or when the loan otherwise becomes well secured and in the process of collection.
Troubled Debt Restructurings	Troubled Debt Restructurings Troubled debt restructurings, or TDRs, are loans where we, for economic or legal reasons related to a borrower’s financial difficulty, grant a concession to the borrower that we would not otherwise grant. We strive to identify borrowers in financial difficulty early and work with them to modify the terms before their loan reaches nonaccrual status. These modified terms generally include extensions of maturity dates at a stated interest rate lower than the current market rate for a new loan with similar risk characteristics, reductions in contractual interest rates or principal deferment. While unusual, there may be instances of principal forgiveness. These modifications are generally for longer term periods that would not be considered insignificant. Additionally, we classify loans where the debt obligation has been discharged through a Chapter 7 Bankruptcy and not reaffirmed as TDRs. We individually evaluate all substandard commercial loans that experienced a forbearance or change in terms agreement, as well as all substandard consumer and residential mortgage loans that entered into an agreement to modify their existing loan to determine if they should be designated as TDRs. All TDRs will be reported as impaired loans for the remaining life of the loan, unless the restructuring agreement specifies an interest rate equal to or greater than the rate that would be accepted at the time of the restructuring for a new loan with comparable risk and it is fully expected that the remaining principal and interest will be collected according to the restructured agreement. Further, all impaired loans are reported as nonaccrual loans unless the loan is a TDR that has met the requirements to be returned to accruing status. TDRs can be returned to accruing status if the ultimate collectability of all contractual amounts due, according to the restructured agreement, is not in doubt and there is a period of a minimum of six months of satisfactory payment performance by the borrower either immediately before or after the restructuring.
Allowance for Loan Losses	Allowance for Loan Losses The ALL reflects our estimates of probable losses inherent in the loan portfolio at the balance sheet date. The methodology for determining the ALL has two main components: evaluation and impairment tests of individual loans and evaluation and impairment tests of certain groups of homogeneous loans with similar risk characteristics. A loan is considered impaired when it is probable that we will be unable to collect all principal and interest payments due according to the original contractual terms of the loan agreement. We individually evaluate all substandard and nonaccrual commercial loans greater than $0.5 million for impairment. TDRs will be reported as an impaired loan for the remaining life of the loan, unless the restructuring agreement specifies an interest rate equal to or greater than the rate that would be accepted at the time of the restructuring for a new loan with comparable risk and it is fully expected that the remaining principal and interest will be collected according to the restructured agreement. For all TDRs, regardless of size, as well as all other impaired loans, we conduct further analysis to determine the probable loss and assign a specific reserve to the loan if deemed appropriate. Specific reserves are established based upon the following three impairment methods: 1) the present value of expected future cash flows discounted at the loan’s original effective interest rate, 2) the loan’s observable market price or 3) the estimated fair value of the collateral if the loan is collateral dependent. Our impairment evaluations consist primarily of the fair value of collateral method because most of our loans are collateral dependent. Collateral values are discounted to consider disposition costs when appropriate. A specific reserve is established or a charge-off is taken if the fair value of the impaired loan is less than the recorded investment in the loan balance. The ALL for homogeneous loans is calculated using a systematic methodology with both a quantitative and a qualitative analysis that is applied on a quarterly basis. The ALL model is comprised of five distinct portfolio segments: 1) Commercial Real Estate, or CRE, 2) Commercial and Industrial, or C&I, 3) Commercial Construction, 4) Consumer Real Estate and 5) Other Consumer. Each segment has a distinct set of risk characteristics monitored by management. We further assess and monitor risk and performance at a more disaggregated level which includes our internal risk rating system for the commercial segments and type of collateral, lien position and loan-to-value, or LTV, for the consumer segments. We first apply historical loss rates to pools of loans with similar risk characteristics. Loss rates are calculated by historical charge-offs that have occurred within each pool of loans over the loss emergence period, or LEP. The LEP is an estimate of the average amount of time from when an event happens that causes the borrower to be unable to pay on a loan until the loss is confirmed through a loan charge-off. In conjunction with our annual review of the ALL assumptions, we have updated our analysis of LEPs for our Commercial and Consumer loan portfolio segments using our loan charge-off history. The analysis showed that the LEP for our C&I, has shortened and our CRE, and Commercial Construction portfolio segments have not changed. We estimate the LEP to be 2 years for C&I, compared to 2.5 years in the prior year, and 3.5 years for both CRE and Commercial Construction. Our analysis showed an LEP for Consumer Real Estate of 3.5 years and Other Consumer of 1.25 years. This compares to 2 years for both Consumer Real Estate and Other Consumer in the prior year when peer data was being utilized to estimate the LEP. We believe that our actual experience captured through our internal analysis better reflects the inherent risk in these portfolios compared to the peer data used in prior years. Another key assumption is the look-back period, or LBP, which represents the historical data period utilized to calculate loss rates. We lengthened the LBP for all Commercial and Consumer portfolio segments in order to capture relevant historical data believed to be reflective of losses inherent in the portfolios. We use 6.5 years for our LBP for all portfolio segments which encompasses our loss experience during the Great Recession and our more recent improved loss experience. After consideration of the historic loss calculations, management applies additional qualitative adjustments so that the ALL is reflective of the inherent losses that exist in the loan portfolio at the balance sheet date. The following qualitative factors are considered in the ALL: 1) Changes in our lending policies and procedures, including underwriting standards, collection, charge-off and recovery practices not considered elsewhere in estimating credit losses; 2) Changes in national, regional, and local economic and business conditions and developments that affect the collectability of the portfolio, including the condition of various market segments; 3) Changes in the nature and volume of our loan portfolio and terms of loans; 4) Changes in the experience, ability and depth of our lending management and staff; 5) Changes in the volume and severity of past due loans, the volume of nonaccrual loans, and the volume and severity of adversely classified or graded loans; 6) Changes in the quality of our loan review system; 7) Changes in the value of the underlying collateral for collateral-dependent loans; 8) The existence and effect of any concentrations of credit and changes in the level of such concentrations; and 9) The effect of external factors such as competition and legal and regulatory requirements on the level of estimated credit losses in our current loan portfolio. The changes made to the ALL assumptions were applied prospectively and did not result in a material change to the total ALL. Lengthening the LBP does increase the historical loss rates and therefore the quantitative component of the ALL. We believe this makes the quantitative component of the ALL more reflective of inherent losses that exist within the loan portfolio, which resulted in a decrease in the qualitative component of the ALL. Loans acquired with evidence of credit deterioration were evaluated and not considered to be significant. The premium or discount estimated through the loan fair value calculation is recognized into interest income on a level yield or straight-line basis over the remaining contractual life of the loans. Additional credit deterioration on acquired loans, in excess of the original credit discount embedded in the fair value determination on the date of acquisition, will be recognized in the ALL through the provision for loan losses. Our ALL Committee meets quarterly to verify the overall adequacy of the ALL. Additionally, on an annual basis, the ALL Committee meets to validate our ALL methodology. This validation includes reviewing the loan segmentation, LEP, LBP and the qualitative framework. As a result of this ongoing monitoring process, we may make changes to our ALL to be responsive to the economic environment.
Bank Owned Life Insurance	Bank Owned Life Insurance We have purchased life insurance policies on certain executive officers and employees. We receive the cash surrender value of each policy upon its termination or benefits are payable upon the death of the insured. Changes in net cash surrender value are recognized in noninterest income or expense in the Consolidated Statements of Net Income.
Premises and Equipment	Premises and Equipment Premises and equipment, including leasehold improvements, are stated at cost less accumulated depreciation. Maintenance and repairs are charged to expense as incurred, while improvements that extend an asset’s useful life are capitalized and depreciated over the estimated remaining life of the asset. Depreciation expense is computed by the straight-line method for financial reporting purposes and accelerated methods for income tax purposes over the estimated useful lives of the particular assets. Management reviews long-lived assets using events and circumstances to determine if and when an asset is evaluated for recoverability. The estimated useful lives for the various asset categories are as follows: 1) Land and Land Improvements Non-depreciating assets 2) Buildings 25 years 3) Furniture and Fixtures 5 years 4) Computer Equipment and Software 5 years or term of license 5) Other Equipment 5 years 6) Vehicles 5 years 7) Leasehold Improvements Lesser of estimated useful life of the asset (generally 15 years unless established otherwise) or the remaining term of the lease, including renewal options in the lease that are reasonably assured of exercise
Restricted Investment in Bank Stock	Restricted Investment in Bank Stock Federal Home Loan Bank, or FHLB, stock is carried at cost and evaluated for impairment based on the ultimate recoverability of the par value. We hold FHLB stock because we are a member of the FHLB of Pittsburgh. The FHLB requires members to purchase and hold a specified level of FHLB stock based upon on the members asset value, level of borrowings and participation in other programs offered. Stock in the FHLB is non-marketable and is redeemable at the discretion of the FHLB. Members do not purchase stock in the FHLB for the same reasons that traditional equity investors acquire stock in an investor-owned enterprise. Rather, members purchase stock to obtain access to the low-cost products and services offered by the FHLB. Unlike equity securities of traditional for-profit enterprises, the stock of the FHLB does not provide its holders with an opportunity for capital appreciation because, by regulation, FHLB stock can only be purchased, redeemed and transferred at par value. Both cash and stock dividends are reported as income in taxable investment securities in the Consolidated Statements of Net Income. FHLB stock is evaluated for OTTI on a quarterly basis. Atlantic Community Bankers’ Bank, or ACBB, stock is carried at cost and evaluated for impairment based on the ultimate recoverability of the carrying value. We do not currently use their membership products and services. We acquired ACBB stock through various mergers of banks that were ACBB members. ACBB stock is evaluated for OTTI on a quarterly basis.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets We have three reporting units: Community Banking, Insurance and Wealth Management. At December 31, 2015, we had goodwill of $291.8 million , including $287.6 million in Community Banking, representing 99 percent of total goodwill, and $4.2 million in Insurance, representing one percent of total goodwill. The carrying value of goodwill is tested annually for impairment each October 1 or more frequently if it is determined that we should do so. We first assess qualitatively whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. Our qualitative assessment considers such factors as macroeconomic conditions, market conditions specifically related to the banking industry, our overall financial performance and various other factors. If we determine that it is more likely than not that the fair value is less than the carrying amount, we proceed to test for impairment. The evaluation for impairment involves comparing the current estimated fair value of each reporting unit to its carrying value, including goodwill. If the current estimated fair value of a reporting unit exceeds its carrying value, no additional testing is required and impairment loss is not recorded. If the estimated fair value of a reporting unit is less than the carrying value, further valuation procedures are performed and could result in impairment of goodwill being recorded. Further valuation procedures would include allocating the estimated fair value to all assets and liabilities of the reporting unit to determine an implied goodwill value. If the implied value of goodwill of a reporting unit is less than the carrying amount of that goodwill, an impairment loss is recognized in an amount equal to that excess. We have core deposit and other intangible assets resulting from acquisitions which are subject to amortization. We determine the amount of identifiable intangible assets based upon independent core deposit and insurance contract analyses at the time of the acquisition. Intangible assets with finite useful lives, consisting primarily of core deposit and customer list intangibles, are amortized using straight-line or accelerated methods over their estimated weighted average useful lives, ranging from 10 to 20 years. Intangible assets with finite useful lives are evaluated for impairment whenever events or changes in circumstances indicate that their carrying amount may not be recoverable.
Variable Interest Entities	Variable Interest Entities Variable interest entities, or VIEs, are legal entities that generally either do not have equity investors with voting rights or that have equity investors that do not provide sufficient financial resources for the entity to support its activities. When an enterprise has both the power to direct the economic activities of the VIE and the obligation to absorb losses of the VIE or the right to receive benefits of the VIE, the entity has a controlling financial interest in the VIE. A VIE often holds financial assets, including loans or receivables, or other property. The company with a controlling financial interest, the primary beneficiary, is required to consolidate the VIE into its consolidated balance sheets. S&T has one wholly-owned trust subsidiary, STBA Capital Trust I, or the Trust, for which it does not absorb a majority of expected losses or receive a majority of the expected residual returns. At its inception in 2008, the Trust issued floating rate trust preferred securities to the Trustee, another financial institution, and used the proceeds from the sale to invest in junior subordinated debt, which is the sole asset of the Trust. The Trust pays dividends on the trust preferred securities at the same rate as the interest we pay on our junior subordinated debt held by the Trust. Because the third-party investors are the primary beneficiaries, the Trust qualifies as a VIE. Accordingly, the Trust and its net assets are not included in our Consolidated Financial Statements. However, the junior subordinated debt issued by S&T is included in our Consolidated Balance Sheets.
Joint Ventures	Joint Ventures We have made investments directly in Low Income Housing Tax Credit, or LIHTC, partnerships formed with third parties. As a limited partner in these operating partnerships, we receive tax credits and tax deductions for losses incurred by the underlying properties. These investments are amortized over a maximum of 10 years , which represents the period that the tax credits will be utilized. We have determined that we are not the primary beneficiary of these investments because the general partners have the power to direct the activities that most significantly impact the economic performance of the partnership and have both the obligation to absorb expected losses and the right to receive benefits.
OREO and Other Repossessed Assets	OREO and Other Repossessed Assets OREO and other repossessed assets are included in other assets in the Consolidated Balance Sheets and are comprised of properties acquired through foreclosure proceedings or acceptance of a deed in lieu of a foreclosure. At the time of foreclosure or acceptance of a deed in lieu of foreclosure, these properties are recorded at the lower of the recorded investment in the loan or fair value less cost to sell. Loan losses arising from the acquisition of any such property initially are charged against the ALL. Subsequently, these assets are carried at the lower of carrying value or current fair value less cost to sell. Gains or losses realized upon disposition of these assets are recorded in other expenses in the Consolidated Statements of Net Income.
Mortgage Servicing Rights	Mortgage Servicing Rights MSRs are recognized as separate assets when commitments to fund a loan to be sold are made. Upon commitment, the MSR is established, which represents the then current estimated fair value of future net cash flows expected to be realized for performing the servicing activities. The estimated fair value of the MSRs is estimated by calculating the present value of estimated future net servicing cash flows, considering expected mortgage loan prepayment rates, discount rates, servicing costs and other economic factors, which are determined based on current market conditions. The expected rate of mortgage loan prepayments is the most significant factor driving the value of MSRs. Increases in mortgage loan prepayments reduce estimated future net servicing cash flows because the life of the underlying loan is reduced. In determining the estimated fair value of MSRs, mortgage interest rates, which are used to determine prepayment rates, are held constant over the estimated life of the portfolio. MSRs are reported in other assets in the Consolidated Balance Sheets and are amortized into noninterest income in the Consolidated Statements of Net Income in proportion to, and over the period of, the estimated future net servicing income of the underlying mortgage loans. MSRs are regularly evaluated for impairment based on the estimated fair value of those rights. MSRs are stratified by certain risk characteristics, primarily loan term and note rate. If temporary impairment exists within a risk stratification tranche, a valuation allowance is established through a charge to income equal to the amount by which the carrying value exceeds the estimated fair value. If it is later determined that all or a portion of the temporary impairment no longer exists for a particular tranche, the valuation allowance is reduced. MSRs are also reviewed for OTTI. OTTI exists when the recoverability of a recorded valuation allowance is determined to be remote, taking into consideration historical and projected interest rates and loan pay-off activity. When this situation occurs, the unrecoverable portion of the valuation allowance is applied as a direct write-down to the carrying value of the MSR. Unlike a valuation allowance, a direct write-down permanently reduces the carrying value of the MSR and the valuation allowance, precluding subsequent recoveries.
Derivative Financial Instruments	Derivative Financial Instruments Interest Rate Swaps In accordance with applicable accounting guidance for derivatives and hedging, all derivatives are recognized as either assets or liabilities on the balance sheet at fair value. Interest rate swaps are contracts in which a series of interest rate flows (fixed and variable) are exchanged over a prescribed period. The notional amounts on which the interest payments are based are not exchanged. These derivative positions relate to transactions in which we enter into an interest rate swap with a commercial customer while at the same time entering into an offsetting interest rate swap with another financial institution. In connection with each transaction, we agree to pay interest to the customer on a notional amount at a variable interest rate and receive interest from the customer on a same notional amount at a fixed rate. At the same time, we agree to pay another financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount. The transaction allows our customer to effectively convert a variable rate loan to a fixed rate loan with us receiving a variable rate. These agreements could have floors or caps on the contracted interest rates. Pursuant to our agreements with various financial institutions, we may receive collateral or may be required to post collateral based upon mark-to-market positions. Beyond unsecured threshold levels, collateral in the form of cash or securities may be made available to counterparties of interest rate swap transactions. Based upon our current positions and related future collateral requirements relating to them, we believe any effect on our cash flow or liquidity position to be immaterial. Derivatives contain an element of credit risk, the possibility that we will incur a loss because a counterparty, which may be a financial institution or a customer, fails to meet its contractual obligations. All derivative contracts with financial institutions may be executed only with counterparties approved by our Asset and Liability Committee, or ALCO, and derivatives with customers may only be executed with customers within credit exposure limits approved by our Senior Loan Committee. Interest rate swaps are considered derivatives, but are not accounted for using hedge accounting. As such, changes in the estimated fair value of the derivatives are recorded in current earnings and included in other noninterest income in the Consolidated Statements of Net Income. Interest Rate Lock Commitments and Forward Sale Contracts In the normal course of business, we sell originated mortgage loans into the secondary mortgage loan market. We also offer interest rate lock commitments to potential borrowers. The commitments are generally for a period of 60 days and guarantee a specified interest rate for a loan if underwriting standards are met, but the commitment does not obligate the potential borrower to close on the loan. Accordingly, some commitments expire prior to becoming loans. We can encounter pricing risks if interest rates increase significantly before the loan can be closed and sold. We may utilize forward sale contracts in order to mitigate this pricing risk. Whenever a customer desires these products, a mortgage originator quotes a secondary market rate guaranteed for that day by the investor. The rate lock is executed between the mortgagee and us and in turn a forward sale contract may be executed between us and the investor. Both the rate lock commitment and the corresponding forward sale contract for each customer are considered derivatives, but are not accounted for using hedge accounting. As such, changes in the estimated fair value of the derivatives during the commitment period are recorded in current earnings and included in mortgage banking in the Consolidated Statements of Net Income.
Allowance for Unfunded Commitments	Allowance for Unfunded Commitments In the normal course of business, we offer off-balance sheet credit arrangements to enable our customers to meet their financing objectives. These instruments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the financial statements. Our exposure to credit loss, in the event the customer does not satisfy the terms of the agreement, equals the contractual amount of the obligation less the value of any collateral. We apply the same credit policies in making commitments and standby letters of credit that are used for the underwriting of loans to customers. Commitments generally have fixed expiration dates, annual renewals or other termination clauses and may require payment of a fee. Because many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The allowance for unfunded commitments is included in other liabilities in the Consolidated Balance Sheets. The allowance for unfunded commitments is determined using a similar methodology as our ALL methodology.
Treasury Stock	Treasury Stock The repurchase of our common stock is recorded at cost. At the time of reissuance, the treasury stock account is reduced using the average cost method. Gains and losses on the reissuance of common stock are recorded in additional paid-in capital, to the extent additional paid-in capital from previous treasury share transactions exists. Any deficiency is charged to retained earnings.
Revenue Recognition	Revenue Recognition We recognize revenues as they are earned based on contractual terms or as services are provided when collectability is reasonably assured. Our principal source of revenue is interest income, which is recognized on an accrual basis. Interest and dividend income, loan fees, trust fees, fees and charges on deposit accounts, insurance commissions and other ancillary income related to our deposits and lending activities are accrued as earned.
Wealth Management Fees	Wealth Management Fees Assets held in a fiduciary capacity by the subsidiary bank, S&T Bank, are not our assets and are therefore not included in our Consolidated Financial Statements. Wealth management fee income is reported in the Consolidated Statements of Net Income on an accrual basis.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation may include stock options and restricted stock which is measured using the fair value method of accounting. The grant date fair value is recognized over the period during which the recipient is required to provide service in exchange for the award. Stock option expense is determined utilizing the Black-Scholes model. Restricted stock expense is determined using the grant date fair value. We estimate expected forfeitures when stock-based awards are granted and record compensation expense only for awards that are expected to vest.
Pensions	Pensions The expense for S&T Bank’s qualified and nonqualified defined benefit pension plans is actuarially determined using the projected unit credit actuarial cost method. It requires us to make economic assumptions regarding future interest rates and asset returns as well as various demographic assumptions. We estimate the discount rate used to measure benefit obligations by applying the projected cash flow for future benefit payments to a yield curve of high-quality corporate bonds available in the marketplace and by employing a model that matches bonds to our pension cash flows. The expected return on plan assets is an estimate of the long-term rate of return on plan assets, which is determined based on the current asset mix and estimates of return by asset class. We recognize in the Consolidated Balance Sheets an asset for the plan’s overfunded status or a liability for the plan’s underfunded status. Gains or losses related to changes in benefit obligations or plan assets resulting from experience different from that assumed are recognized as other comprehensive income (loss) in the period in which they occur. To the extent that such gains or losses exceed ten percent of the greater of the projected benefit obligation or plan assets, they are recognized as a component of pension costs over the future service periods of actively employed plan participants. The funding policy for the qualified plan is to contribute an amount each year that is at least equal to the minimum required contribution as determined under the Pension Protection Act of 2006 and the Bipartisan Budget Act of 2015, but not more than the maximum amount permissible for taxable plan sponsors. Our nonqualified plans are unfunded.
Marketing Costs	Marketing Costs We expense all marketing-related costs, including advertising costs, as incurred.
Income Taxes	Income Taxes We estimate income tax expense based on amounts expected to be owed to the tax jurisdictions where we conduct business. On a quarterly basis, management assesses the reasonableness of our effective tax rate based upon our current estimate of the amount and components of net income, tax credits and the applicable statutory tax rates expected for the full year. We classify interest and penalties as an element of tax expense. Deferred income tax assets and liabilities are determined using the asset and liability method and are reported in other assets or other liabilities, as appropriate, in the Consolidated Balance Sheets. Under this method, the net deferred tax asset or liability is based on the tax effects of the differences between the book and tax basis of assets and liabilities and recognizes enacted changes in tax rate and laws. When deferred tax assets are recognized, they are subject to a valuation allowance based on management’s judgment as to whether realization is more likely than not. Accrued taxes represent the net estimated amount due to taxing jurisdictions and are reported in other assets or other liabilities, as appropriate, in the Consolidated Balance Sheets. We evaluate and assess the relative risks and appropriate tax treatment of transactions and filing positions after considering statutes, regulations, judicial precedent and other information and maintain tax accruals consistent with the evaluation of these relative risks and merits. Changes to the estimate of accrued taxes occur periodically due to changes in tax rates, interpretations of tax laws, the status of examinations being conducted by taxing authorities and changes to statutory, judicial and regulatory guidance. These changes, when they occur, can affect deferred taxes and accrued taxes, as well as the current period’s income tax expense and can be significant to our operating results. Tax positions are recognized as a benefit only if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit that is greater than 50 percent likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded.
Earnings Per Share	Earnings Per Share Basic earnings per share, or EPS, is calculated using the two-class method to determine income allocated to common shareholders. Unvested share-based payment awards that contain nonforfeitable rights to dividends are considered participating securities under the two-class method. Income allocated to common shareholders is then divided by the weighted average number of common shares outstanding during the period. Potentially dilutive securities are excluded from the basic EPS calculation. Diluted EPS is calculated under the more dilutive of either the treasury stock method or the two-class method. Under the treasury stock method, the weighted average number of common shares outstanding is increased by the potentially dilutive common shares. For the two-class method, diluted EPS is calculated for each class of shareholders using the weighted average number of shares attributed to each class. Potentially dilutive common shares are common stock equivalents relating to our outstanding warrants, stock options and restricted stock.
Recently Adopted Accounting Standards Updates, or ASU	Recently Adopted Accounting Standards Updates, or ASU Repurchase-To-Maturity Transactions, Repurchase Financings, and Disclosures In June 2014, the Financial Accounting Standards Board, or FASB, issued ASU No. 2014-11, Repurchase-to-Maturity Transactions, Repurchase Financings, and Disclosures which introduces two accounting changes to the Transfers and Servicing guidance (Topic 860). Repurchase-to-maturity transactions will be accounted for as secured borrowing transactions on the balance sheet and for repurchase financing arrangements, an entity will account separately for a transfer of a financial asset executed contemporaneously with a repurchase agreement with the same counterparty. This will also generally result in secured borrowing accounting for the repurchase agreement. With respect to disclosures, a transferor is required to disclose information about transactions accounted for as a sale in which the transferor retains substantially all of the exposure to the economic return on the transferred financial assets through an agreement with the transferee. Additionally, new disclosures are required for repurchase agreements, securities lending transactions, and repurchase-to-maturity transactions that are accounted for as secured borrowings. The new disclosure for transactions accounted for as secured borrowings was required for interim periods beginning after March 15, 2015. These new disclosures are included in Note 16. Borrowings. The adoption of this ASU had no impact on our results of operations or financial position. Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity In April 2014, the FASB issued ASU No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, which changes the criteria for determining which disposals can be presented as discontinued operations and modifies related disclosure requirements. The guidance applies to all entities that dispose of components. It will significantly change current practices for assessing discontinued operations and affect an entity’s income and earnings per share from continuing operations. An entity is required to reclassify assets and liabilities of a discontinued operation that are classified as held for sale or disposed of in the current period for all comparative periods presented. The ASU requires that an entity present in the statement of cash flows or disclose in a note either total operating and investing cash flows for discontinued operations, or depreciation, amortization, capital expenditures and significant operating and investing noncash items related to discontinued operations. Additional disclosures are required when an entity retains significant continuing involvement with a discontinued operation after its disposal, including the amount of cash flows to and from a discontinued operation. The new standard applies prospectively after the effective date of December 15, 2014, and early adoption was permitted. The adoption of this ASU had no impact on our results of operations or financial position. Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure In January 2014, the FASB issued ASU No. 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure. The ASU clarifies that an in substance repossession or foreclosure has occurred and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan, upon either the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure. Interim and annual disclosure is required of both the amount of foreclosed residential real estate property held by the creditor and the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure. The new standard was effective using either the modified retrospective transition method or a prospective transition method for fiscal years and interim periods within those years, beginning after December 15, 2014, and early adoption was permitted. The adoption of this ASU had no impact on our results of operations or financial position. Accounting for Investments in Qualified Affordable Housing Projects In January 2014, the FASB issued ASU No. 2014-01, Accounting for Investments in Qualified Affordable Housing Projects. The ASU permits reporting entities to make an accounting policy election to account for investments in qualified affordable housing projects using the proportional amortization method if certain conditions are met. The proportional amortization method permits the amortization of the initial cost of the investment in proportion to the tax credits and other tax benefits received, and recognizes the net investment performance in the income statement as a component of income tax expense (benefit). The new standard was effective retrospectively for fiscal years and interim periods within those years, beginning after December 15, 2014, and early adoption was permitted. This ASU did not have a material impact on our results of operations or financial position. We did not adopt the proportional amortization method. Refer to Note 14 for additional disclosure. Recently Issued Accounting Standards Updates not yet Adopted Accounting for Financial Instruments – Overall: Classification and Measurement In January 2016, the FASB issued ASU No. 2016-01, Accounting for Financial Instruments – Overall: Classification and Measurement (Subtopic 825-10). Amendments within ASU No. 2016-01 that relate to non-public entities have been excluded from this presentation. The amendments in this ASU No. 2016-01 address the following: 1) require equity investments to be measured at fair value with changes in fair value recognized in net income; 2) simplify the impairment assessment of equity investments without readily-determinable fair values by requiring a qualitative assessment to identify impairment; 3) eliminate the requirement to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; 4) require entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; 5) require separate presentation in other comprehensive income for the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; 6) require separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (that is, securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; and 7) clarify that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets. We anticipate that this ASU would have a significant impact on our financial statements and disclosures primarily as it relates to recognizing the fair value changes for equity securities in net income rather than an adjustment to equity through other comprehensive income. Business Combinations – Simplifying the Accounting for Measurement Period Adjustments In September 2015, the FASB issued ASU No. 2015-16, Business Combinations – Simplifying the Accounting for Measurement Period Adjustments (Topic 805): The amendments in this ASU No. 2015-16 eliminate the requirement to retrospectively adjust the financial statements for measurement-period adjustments as if they were known at the acquisition date, but are recognized in the reporting period in which they are determined. Additional disclosures are required about the impact on current-period income statement line items of adjustments that would have been recognized in prior periods if that information had been revised. The measurement period is a reasonable time period after the acquisition date when the acquirer may adjust the provisional amounts recognized for a business combination if the necessary information is not available by the end of the reporting period in which the acquisition occurs. The measurement periods cannot continue for more than one year from the acquisition date. The standard is effective for annual periods and interim periods beginning after December 15, 2015. We do not expect that this ASU would have a material impact on our results of operations or financial position. Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date. This ASU defers the effective date of ASU No. 2014-09 for all entities by one year. The new revenue pronouncement creates a single source of revenue guidance for all companies in all industries and is more principles-based than current revenue guidance. The pronouncement provides a five-step model for a company to recognize revenue when it transfers control of goods or services to customers at an amount that reflects the consideration to which it expects to be entitled in exchange for those goods or services. The five steps are, (1) identify the contract with the customer, (2) identify the separate performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the separate performance obligations and (5) recognize revenue when each performance obligation is satisfied. The update is effective for interim and annual reporting periods in fiscal years beginning after December 15, 2017. Early adoption is permitted as of the original effective date for interim and annual reporting periods in fiscal years beginning after December 15, 2016. We are currently evaluating the impact of the adoption of this ASU on our results of operations and financial position. Intangibles – Goodwill and Other – Internal-Use Software: Customer's Accounting for Fees Paid in a Cloud Computing Arrangement In April 2015, the FASB issued ASU No. 2015-05, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer's Accounting for Fees Paid in a Cloud Computing Arrangement. The main provisions of ASU No. 2015-05 provide a basis for evaluating whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, then the arrangement should be accounted for as a service contract. The standard is effective for annual periods and interim periods beginning after December 15, 2015. We do not expect that this ASU would have a material impact on our results of operations or financial position. Interest – Imputation of Interest: Simplifying the Presentation of Debt Issuance Costs In April 2015, the FASB issued ASU No. 2015-03, Interest – Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs. The amendments in this ASU require that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2015. In September 2015, the FASB issued ASU No. 2015-15, Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements. ASU No. 2015-15 amends the Securities and Exchange Commission (SEC) Content in Subtopic 835-30 by adding SEC paragraph 835-30-S35-1, Interest--Imputation of Interest Subsequent Measurement and paragraph 830-30-S45-1, Other Presentation Matters. These paragraphs were added because ASU No. 2015-03 issued in April 2015 does not address presentation or subsequent measurement of debt issuance costs related to "line-of-credit arrangements." We do not expect that these ASU amendments would have a material impact on our results of operations or financial position. Consolidation: Amendments to the Consolidation Analysis In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis. The amendments in this ASU affect reporting entities that are required to evaluate whether they should consolidate certain legal entities. All legal entities are subject to reevaluation under the revised consolidation model. Specifically, the amendments: 1) modify the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities, 2) eliminate the presumption that a general partner should consolidate a limited partnership, 3) affect the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships and 4) provide a scope exception from consolidation guidance for reporting entities with interests in legal entities that are required to comply with or operate in accordance with requirements that are similar to those in Rule 2A-7 of the Investment Company Act of 1940 for registered money market funds. The amendments in this ASU are effective for public business entities for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. We are currently evaluating the impact that these amendments may have on our consolidated financial statements. We do not expect that this ASU would have a material impact on our results of operations or financial position. Income Statement – Extraordinary and Unusual Items: Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary In January 2015, the FASB issued ASU No. 2015-01, Income Statement – Extraordinary and Unusual Items (Subtopic 225-20): Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary. The amendments in this ASU No. 2015-01 eliminate from GAAP the concept of extraordinary items and eliminate the requirements for reporting entities to consider whether an underlying event or transaction is extraordinary. The presentation and disclosure guidance for items that are unusual in nature or occur infrequently will be retained and will be expanded to include items that are both unusual in nature and infrequently occurring. The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2015. We do not expect that this ASU would have a material impact on our results of operations or financial position.
Allowance for Loan Losses by Portfolio	We maintain an ALL at a level determined to be adequate to absorb estimated probable credit losses inherent in the loan portfolio as of the balance sheet date. We develop and document a systematic ALL methodology based on the following portfolio segments: 1) CRE, 2) C&I, 3) Commercial Construction, 4) Consumer Real Estate and 5) Other Consumer. The following are key risks within each portfolio segment: CRE —Loans secured by commercial purpose real estate, including both owner occupied properties and investment properties for various purposes such as hotels, strip malls and apartments. Operations of the individual projects as well as global cash flows of the debtors are the primary sources of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type as well as the business prospects of the lessee, if the project is not owner occupied. C&I —Loans made to operating companies or manufacturers for the purpose of production, operating capacity, accounts receivable, inventory or equipment financing. Cash flow from the operations of the company is the primary source of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the industry of the company. Collateral for these types of loans often do not have sufficient value in a distressed or liquidation scenario to satisfy the outstanding debt. Commercial Construction —Loans made to finance construction of buildings or other structures, as well as to finance the acquisition and development of raw land for various purposes. While the risk of these loans is generally confined to the construction period, if there are problems, the project may not be complete, and as such, may not provide sufficient cash flow on its own to service the debt or have sufficient value in a liquidation to cover the outstanding principal. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the type of project and the experience and resources of the developer. Consumer Real Estate —Loans secured by first and second liens such as home equity loans, home equity lines of credit and 1-4 family residences, including purchase money mortgages. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The state of the local housing market can also have a significant impact on this segment because low demand and/or declining home values can limit the ability of borrowers to sell a property and satisfy the debt. Other Consumer —Loans made to individuals that may be secured by assets other than 1-4 family residences, as well as unsecured loans. This segment includes auto loans, unsecured loans and lines and credit cards. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The value of the collateral, if there is any, is less likely to be a source of repayment due to less certain collateral values. We further assess risk within each portfolio segment by pooling loans with similar risk characteristics. For the commercial loan classes, the most important indicator of risk is the internally assigned risk rating, including pass, special mention and substandard. Consumer loans are pooled by type of collateral, lien position and LTV ratio for Consumer Real Estate loans. Historical loss rates are applied to these loan pools to determine the reserve for loans collectively evaluated for impairment. The ALL methodology for groups of loans collectively evaluated for impairment is comprised of both a quantitative and qualitative analysis. A key assumption in the quantitative component of the reserve is LEP. The LEP is an estimate of the average amount of time from the point at which a loss is incurred on a loan to the point at which the loss is confirmed. Another key assumption is LBP, which represents the historical data period utilized to calculate loss rates. Management monitors various credit quality indicators for both the commercial and consumer loan portfolios, including delinquency, nonperforming status and changes in risk ratings on a monthly basis.
Loan Credit Risk Rating	We continually monitor the commercial loan portfolio through an internal risk rating system. Loan risk ratings are assigned based upon the creditworthiness of the borrower and are reviewed on an ongoing basis according to our internal policies. Loans within the pass rating generally have a lower risk of loss than loans risk rated as special mention and substandard. Our risk ratings are consistent with regulatory guidance and are as follows: Pass —The loan is currently performing and is of high quality. Special Mention —A special mention loan has potential weaknesses that warrant management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects or in the strength of our credit position at some future date. Economic and market conditions, beyond the borrower’s control, may in the future necessitate this classification. Substandard —A substandard loan is not adequately protected by the net worth and/or paying capacity of the borrower or by the collateral pledged, if any. Substandard loans have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. These loans are characterized by the distinct possibility that we will sustain some loss if the deficiencies are not corrected.

Summary of Significant Accoun37

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Estimated Useful Lives for Various Asset	The estimated useful lives for the various asset categories are as follows: 1) Land and Land Improvements Non-depreciating assets 2) Buildings 25 years 3) Furniture and Fixtures 5 years 4) Computer Equipment and Software 5 years or term of license 5) Other Equipment 5 years 6) Vehicles 5 years 7) Leasehold Improvements Lesser of estimated useful life of the asset (generally 15 years unless established otherwise) or the remaining term of the lease, including renewal options in the lease that are reasonably assured of exercise

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Summary of Consideration, Assets Acquired and Liabilities Assumed	The following table summarizes total consideration, assets acquired and liabilities assumed as of December 31, 2015: (dollars in thousands) Consideration Paid Cash $ 29,510 Common stock 142,469 Fair Value of Total Consideration $ 171,979 Fair Value of Assets Acquired Cash and cash equivalents $ 13,163 Securities and other investments 11,502 Loans 788,687 Bank owned life insurance 15,974 Premises and equipment 10,855 Core deposit intangible 5,713 Other assets 18,994 Total Assets Acquired 864,888 Fair Value of Liabilities Assumed Deposits 722,308 Borrowings 82,286 Other liabilities 4,259 Total Liabilities Assumed 808,853 Total Fair Value of Identifiable Net Assets 56,035 Goodwill $ 115,944
Schedule of Pro Forma Information	The following table presents unaudited pro forma financial information which combines the historical consolidated statements of income of S&T and Integrity to give effect to the Merger as if it had occurred on January 1, 2014, for the periods presented. Unaudited Pro Forma Information (dollars in thousands, except per share data) 2015 2014 Total revenue (1) $ 240,581 $ 232,635 Net income (2) $ 68,850 $ 70,001 Earnings per common share: (2) Basic $ 1.78 $ 2.02 Diluted $ 1.77 $ 2.02 (1) Total pro forma revenue is defined as net interest income plus non-interest income, excluding gains and losses on sales of investment securities available-for-sale. ( 2) Excludes merger expenses

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Reconciles Numerators and Denominators of Basic Earnings Per Share and Diluted Earnings Per Share	The following table reconciles the numerators and denominators of basic and diluted EPS: Years ended December 31, (dollars in thousands, except share and per share data) 2015 2014 2013 Numerator for Earnings per Common Share—Basic: Net income $ 67,081 $ 57,910 $ 50,539 Less: Income allocated to participating shares 280 165 147 Net Income Allocated to Common Shareholders $ 66,801 $ 57,745 $ 50,392 Numerator for Earnings per Common Share—Diluted: Net income $ 67,081 $ 57,910 $ 50,539 Denominators: Weighted Average Common Shares Outstanding—Basic 33,812,990 29,683,103 29,647,231 Add: Dilutive potential common shares 35,092 25,621 35,322 Denominator for Treasury Stock Method—Diluted 33,848,082 29,708,724 29,682,553 Weighted Average Common Shares Outstanding—Basic 33,812,990 29,683,103 29,647,231 Add: Average participating shares outstanding 141,558 84,918 86,490 Denominator for Two-Class Method—Diluted 33,954,548 29,768,021 29,733,721 Earnings per common share—basic $ 1.98 $ 1.95 $ 1.70 Earnings per common share—diluted $ 1.98 $ 1.95 $ 1.70 Warrants considered anti-dilutive excluded from dilutive potential common shares - exercise price $31.53 per share, expires January 2019 517,012 517,012 517,012 Stock options considered anti-dilutive excluded from dilutive potential common shares — 419,538 619,418 Restricted stock considered anti-dilutive excluded from dilutive potential common shares 106,466 59,297 51,169

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables present our assets and liabilities that are measured at fair value on a recurring basis by fair value hierarchy level at December 31, 2015 and 2014. There were no transfers between Level 1 and Level 2 for items measured at fair value on a recurring basis during the periods presented. December 31, 2015 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Securities available-for-sale: U.S. Treasury securities $ — $ 14,941 $ — $ 14,941 Obligations of U.S. government corporations and agencies — 263,303 — 263,303 Collateralized mortgage obligations of U.S. government corporations and agencies — 128,835 — 128,835 Residential mortgage-backed securities of U.S. government corporations and agencies — 40,125 — 40,125 Commercial mortgage-backed securities of U.S. government corporations and agencies — 69,204 — 69,204 Obligations of states and political subdivisions — 134,886 — 134,886 Marketable equity securities — 9,669 — 9,669 Total securities available-for-sale — 660,963 — 660,963 Trading securities held in a Rabbi Trust 4,021 — — 4,021 Total securities 4,021 660,963 — 664,984 Derivative financial assets: Interest rate swaps — 11,295 — 11,295 Interest rate lock commitments — 261 — 261 Total Assets $ 4,021 $ 672,519 $ — $ 676,540 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 11,276 $ — $ 11,276 Forward sale contracts — 5 — 5 Total Liabilities $ — $ 11,281 $ — $ 11,281 December 31, 2014 (dollars in thousands) Level 1 Level 2 Level 3 Total ASSETS Securities available-for-sale: U.S. Treasury securities $ — $ 14,880 $ — $ 14,880 Obligations of U.S. government corporations and agencies — 269,285 — 269,285 Collateralized mortgage obligations of U.S. government corporations and agencies — 118,006 — 118,006 Residential mortgage-backed securities of U.S. government corporations and agencies — 46,668 — 46,668 Commercial mortgage-backed securities of U.S. government corporations and agencies — 39,673 — 39,673 Obligations of states and political subdivisions — 142,702 — 142,702 Marketable equity securities 178 8,881 — 9,059 Total securities available-for-sale 178 640,095 — 640,273 Trading securities held in a Rabbi Trust 3,456 — — 3,456 Total securities 3,634 640,095 — 643,729 Derivative financial assets: Interest rate swaps — 12,981 — 12,981 Interest rate lock commitments — 235 — 235 Total Assets $ 3,634 $ 653,311 $ — $ 656,945 LIABILITIES Derivative financial liabilities: Interest rate swaps $ — $ 12,953 $ — $ 12,953 Forward Sale Contracts — 57 57 Total Liabilities $ — $ 13,010 $ — $ 13,010
Assets Measured at Fair Value on Nonrecurring Basis by Fair Value Hierarchy	The following table presents our assets that are measured at fair value on a nonrecurring basis by the fair value hierarchy level as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total ASSETS (1) Impaired loans — — 9,373 9,373 — — 12,916 12,916 Other real estate owned — — 158 158 — — 117 117 Mortgage servicing rights — — 3,396 3,396 — — 2,934 2,934 Total Assets $ — $ — $ 12,927 $ 12,927 $ — $ — $ 15,967 $ 15,967 (1) This table presents only the nonrecurring items that are recorded at fair value in our financial statements.
Carrying Values and Fair Values of Financial Instruments	The carrying values and fair values of our financial instruments at December 31, 2015 and 2014 are presented in the following tables: Fair Value Measurements at December 31, 2015 (dollars in thousands) Carrying Value (1) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 99,399 $ 99,399 $ 99,399 $ — $ — Securities available-for-sale 660,963 660,963 — 660,963 — Loans held for sale 35,321 35,500 — — 35,500 Portfolio loans, net of unearned income 5,027,612 5,001,004 — — 5,001,004 Bank owned life insurance 70,175 70,175 — 70,175 — FHLB and other restricted stock 23,032 23,032 — — 23,032 Trading securities held in a Rabbi Trust 4,021 4,021 4,021 — — Mortgage servicing rights 3,237 3,396 — — 3,396 Interest rate swaps 11,295 11,295 — 11,295 — Interest rate lock commitments 261 261 — 261 — LIABILITIES Deposits $ 4,876,611 $ 4,881,718 $ — $ — $ 4,881,718 Securities sold under repurchase agreements 62,086 62,086 — — 62,086 Short-term borrowings 356,000 356,000 — — 356,000 Long-term borrowings 117,043 117,859 — — 117,859 Junior subordinated debt securities 45,619 45,619 — — 45,619 Interest rate swaps 11,276 11,276 — 11,276 — Forward sale contracts 5 5 — 5 — (1) As reported in the Consolidated Balance Sheets Fair Value Measurements at December 31, 2014 (dollars in thousands) Carrying Value (1) Total Level 1 Level 2 Level 3 ASSETS Cash and due from banks, including interest-bearing deposits $ 109,580 $ 109,580 $ 109,580 $ — $ — Securities available-for-sale 640,273 640,273 178 640,095 — Loans held for sale 2,970 2,991 — — 2,991 Portfolio loans, net of unearned income 3,868,746 3,827,634 — — 3,827,634 Bank owned life insurance 62,252 62,252 — 62,252 — FHLB and other restricted stock 15,135 15,135 — — 15,135 Trading securities held in a Rabbi Trust 3,456 3,456 3,456 — — Mortgage servicing rights 2,817 2,934 — — 2,934 Interest rate swaps 12,981 12,981 — 12,981 — Interest rate lock commitments 235 235 — 235 — LIABILITIES Deposits $ 3,908,842 $ 3,910,342 $ — $ — $ 3,910,342 Securities sold under repurchase agreements 30,605 30,605 — — 30,605 Short-term borrowings 290,000 290,000 — — 290,000 Long-term borrowings 19,442 20,462 — — 20,462 Junior subordinated debt securities 45,619 45,619 — — 45,619 Interest rate swaps 12,953 12,953 — 12,953 — Forward sale contracts 57 57 — 57 — (1) As reported in the Consolidated Balance Sheets

Securities Available-for-Sale (

Securities Available-for-Sale (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Composition of Securities Available-for-Sale	The following tables present the amortized cost and fair value of available-for-sale securities as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. Treasury securities $ 14,914 $ 27 $ — $ 14,941 $ 14,873 $ 7 $ — $ 14,880 Obligations of U.S. government corporations and agencies 262,045 1,825 (567 ) 263,303 268,029 2,334 (1,078 ) 269,285 Collateralized mortgage obligations of U.S. government corporations and agencies 128,458 693 (316 ) 128,835 116,897 1,257 (148 ) 118,006 Residential mortgage-backed securities of U.S. government corporations and agencies 39,185 1,091 (151 ) 40,125 45,274 1,548 (154 ) 46,668 Commercial mortgage-backed securities of U.S. government corporations and agencies 69,697 183 (676 ) 69,204 39,834 232 (393 ) 39,673 Obligations of states and political subdivisions 128,904 5,988 (6 ) 134,886 136,977 5,789 (64 ) 142,702 Debt Securities 643,203 9,807 (1,716 ) 651,294 621,884 11,167 (1,837 ) 631,214 Marketable equity securities 7,579 2,090 — 9,669 7,579 1,480 — 9,059 Total $ 650,782 $ 11,897 $ (1,716 ) $ 660,963 $ 629,463 $ 12,647 $ (1,837 ) $ 640,273
Schedule of Gross and Net Realized Gains and Losses on Sale of Securities	The following table shows the composition of gross and net realized gains and losses for the periods presented: Years ended December 31, (dollars in thousands) 2015 2014 2013 Gross realized gains $ — $ 41 $ 5 Gross realized losses (34 ) — — Net Realized (Losses) Gains $ (34 ) $ 41 $ 5
Fair Value and Age of Gross Unrealized Losses by Investment Category	The following tables present the fair value and the age of gross unrealized losses by investment category as of the dates presented: December 31, 2015 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Losses Number of Securities Fair Unrealized Losses Number of Securities Fair Unrealized Losses Obligations of U.S. government corporations and agencies 10 $ 88,584 $ (379 ) 2 $ 14,542 $ (188 ) 12 $ 103,126 $ (567 ) Collateralized mortgage obligations of U.S. government corporations and agencies 6 61,211 (316 ) — — — 6 61,211 (316 ) Residential mortgage-backed securities of U.S. government corporations and agencies 1 7,993 (151 ) — — — 1 7,993 (151 ) Commercial mortgage-backed securities of U.S. government corporations and agencies 5 50,839 (450 ) 1 9,472 (226 ) 6 60,311 (676 ) Obligations of states and political subdivisions 1 5,370 (6 ) — — — 1 5,370 (6 ) Total Temporarily Impaired Securities 23 $ 213,997 $ (1,302 ) 3 $ 24,014 $ (414 ) 26 $ 238,011 $ (1,716 ) December 31, 2014 Less Than 12 Months 12 Months or More Total (dollars in thousands) Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses Obligations of U.S. government corporations and agencies 4 $ 39,745 $ (207 ) 8 $ 63,149 $ (871 ) 12 $ 102,894 $ (1,078 ) Collateralized mortgage obligations of U.S. government corporations and agencies 1 9,323 (148 ) — — — 1 9,323 (148 ) Residential mortgage-backed securities of U.S. government corporations and agencies — — — 1 8,982 (154 ) 1 8,982 (154 ) Commercial mortgage-backed securities of U.S. government corporations and agencies 1 9,998 (25 ) 2 20,640 (368 ) 3 30,638 (393 ) Obligations of states and political subdivisions 1 263 (1 ) 2 10,756 (63 ) 3 11,019 (64 ) Total Temporarily Impaired Securities 7 $ 59,329 $ (381 ) 13 $ 103,527 $ (1,456 ) 20 $ 162,856 $ (1,837 )
Unrealized Gain (Loss) on Investments	The following table displays net unrealized gains and losses, net of tax on securities available for sale included in accumulated other comprehensive income/(loss) for the periods presented: December 31, 2015 December 31, 2014 (dollars in thousands) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains (Losses) Gross Unrealized Gains Gross Unrealized Losses Net Unrealized Gains (Losses) Total unrealized gains (losses) on securities available for sale $ 11,897 $ (1,716 ) $ 10,181 $ 12,647 $ (1,837 ) $ 10,810 Income tax expense (benefit) 4,164 (601 ) 3,563 4,426 (643 ) 3,783 Net unrealized gains (losses), net of tax included in accumulated other comprehensive income(loss) $ 7,733 $ (1,115 ) $ 6,618 $ 8,221 $ (1,194 ) $ 7,027
Amortized Cost and Fair Value of Available-for-Sale Securities	The amortized cost and fair value of securities available-for-sale at December 31, 2015 by contractual maturity are included in the table below. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. December 31, 2015 (dollars in thousands) Amortized Cost Fair Value Due in one year or less $ 46,329 $ 46,510 Due after one year through five years 222,838 224,334 Due after five years through ten years 56,934 58,793 Due after ten years 79,762 83,493 405,863 413,130 Collateralized mortgage obligations of U.S. government corporations and agencies 128,458 128,835 Residential mortgage-backed securities of U.S. government corporations and agencies 39,185 40,125 Commercial mortgage-backed securities of U.S. government corporations and agencies 69,697 69,204 Debt Securities 643,203 651,294 Marketable equity securities 7,579 9,669 Total $ 650,782 $ 660,963

Loans and Loans Held for Sale (

Loans and Loans Held for Sale (Tables)	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Composition of Loans	The following table indicates the composition of the acquired and originated loans as of the dates presented: December 31, (dollars in thousands) 2015 2014 Commercial Commercial real estate $ 2,166,603 $ 1,682,236 Commercial and industrial 1,256,830 994,138 Commercial construction 413,444 216,148 Total Commercial Loans 3,836,877 2,892,522 Consumer Residential mortgage 639,372 489,586 Home equity 470,845 418,563 Installment and other consumer 73,939 65,567 Consumer construction 6,579 2,508 Total Consumer Loans 1,190,735 976,224 Total Portfolio Loans 5,027,612 3,868,746 Loans held for sale 35,321 2,970 Total Loans $ 5,062,933 $ 3,871,716
Restructured Loans for Periods Presented	The following table summarizes the restructured loans as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Performing TDRs Nonperforming TDRs Total TDRs Performing TDRs Nonperforming TDRs Total TDRs Commercial real estate $ 6,822 $ 3,548 $ 10,370 $ 16,939 $ 2,180 $ 19,119 Commercial and industrial 6,321 1,570 7,891 8,074 356 8,430 Commercial construction 5,013 1,265 6,278 5,736 1,869 7,605 Residential mortgage 2,590 665 3,255 2,839 459 3,298 Home equity 3,184 523 3,707 3,342 562 3,904 Installment and other consumer 25 88 113 53 10 63 Total $ 23,955 $ 7,659 $ 31,614 $ 36,983 $ 5,436 $ 42,419
Restructured Loans for Periods Stated	The following tables present the restructured loans for the 12 months ended December 31: 2015 (dollars in thousands) Number of Loans Pre-Modification Outstanding Recorded Investment (1) Post-Modification Outstanding Recorded Investment (1) Total Difference in Recorded Investment Commercial real estate Principal deferral 2 $ 2,851 $ 1,841 $ (1,010 ) Maturity date extension 3 438 427 (11 ) Commercial and industrial Principal deferral 6 661 363 (298 ) Maturity date extension 2 824 728 (96 ) Commercial construction Maturity date extension 3 1,434 1,432 (2 ) Residential mortgage Maturity date extension 8 545 265 (280 ) Maturity date extension and interest rate reduction 1 207 205 (2 ) Chapter 7 bankruptcy (2) 7 428 226 (202 ) Home equity Maturity date extension 1 71 70 (1 ) Maturity date extension and interest rate reduction 3 203 201 (2 ) Chapter 7 bankruptcy (2) 23 619 576 (43 ) Installment and other consumer Chapter 7 bankruptcy (2) 1 9 4 (5 ) Total by Concession Type Principal deferral 8 3,512 2,204 (1,308 ) Maturity date extension and interest rate reduction 4 410 406 (4 ) Maturity date extension 17 3,312 2,922 (390 ) Chapter 7 bankruptcy (2) 31 1,056 806 (250 ) Total 60 $ 8,290 $ 6,338 $ (1,952 ) (1) Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Chapter 7 bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed. 2014 (dollars in thousands) Number of Loans Pre-Modification Outstanding Recorded Investment ( 1) Post-Modification Outstanding Recorded Investment (1 ) Total Difference in Recorded Investment Commercial real estate Principal deferral 4 $ 1,991 $ 1,965 $ (26 ) Commercial and industrial Principal deferral 2 381 356 (25 ) Commercial construction Maturity date extension 1 1,019 974 (45 ) Residential mortgage Chapter 7 bankruptcy (2) 9 651 634 (17 ) Home Equity Maturity date extension and interest rate reduction 2 96 95 (1 ) Maturity date extension 6 349 348 (1 ) Chapter 7 bankruptcy (2) 15 432 382 (50 ) Installment and other consumer Chapter 7 bankruptcy (2) 5 30 23 (7 ) Total by Concession Type Principal deferral 6 2,372 2,321 (51 ) Maturity date extension and interest rate reduction 2 96 95 (1 ) Maturity date extension 7 1,368 1,322 (46 ) Chapter 7 bankruptcy (2) 29 1,113 1,039 (74 ) Total 44 $ 4,949 $ 4,777 $ (172 ) (1) Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end. (2) Chapter 7 bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed.
Summary of Nonperforming Assets of Defaulted TDRs	The following tables present a summary of TDRs which defaulted during the years ended December 31, 2015 and 2014 that had been restructured within the last 12 months prior to defaulting: Defaulted TDRs For the For the (dollars in thousands) Number of Defaults Recorded Investment Number of Defaults Recorded Investment Commercial real estate — $ — — $ — Commercial and industrial — — — — Residential real estate — — 1 20 Home equity — — 2 44 Total — $ — 3 $ 64
Summary of Nonperforming Assets	The following table is a summary of nonperforming assets as of the dates presented: December 31, (dollars in thousands) 2015 2014 Nonperforming Assets Nonaccrual loans $ 27,723 $ 7,021 Nonaccrual TDRs 7,659 5,436 Total nonaccrual loans 35,382 12,457 OREO 354 166 Total Nonperforming Assets $ 35,736 $ 12,623
Summary of Aggregate Amount of Loans	The following table presents a summary of the aggregate amount of loans to any such persons as of December 31: (dollars in thousands) 2015 2014 Balance at beginning of year $ 27,368 $ 23,848 New loans 24,743 27,799 Repayments (27,594 ) (24,279 ) Balance at End of Year $ 24,517 $ 27,368

Allowance for Loan Losses (Tabl

Allowance for Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Age Analysis of Past Due Loans Segregated by Class of Loans	The following tables present the age analysis of past due loans segregated by class of loans as of the dates presented: December 31, 2015 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due Non- performing Total Past Due Loans Total Loans Commercial real estate $ 2,145,655 $ 11,602 $ 627 $ 8,719 $ 20,948 $ 2,166,603 Commercial and industrial 1,244,802 2,453 296 9,279 12,028 1,256,830 Commercial construction 401,084 3,517 90 8,753 12,360 413,444 Residential mortgage 631,085 1,728 930 5,629 8,287 639,372 Home equity 465,055 2,365 523 2,902 5,790 470,845 Installment and other consumer 73,486 242 111 100 453 73,939 Consumer construction 6,579 — — — — 6,579 Loans held for sale 35,179 94 48 — 142 35,321 Total $ 5,002,925 $ 22,001 $ 2,625 $ 35,382 $ 60,008 $ 5,062,933 December 31, 2014 (dollars in thousands) Current 30-59 Days Past Due 60-89 Days Past Due Non- performing Total Past Due Loans Total Loans Commercial real estate $ 1,674,930 $ 2,548 $ 323 $ 4,435 $ 7,306 $ 1,682,236 Commercial and industrial 991,136 1,227 153 1,622 3,002 994,138 Commercial construction 214,174 — — 1,974 1,974 216,148 Residential mortgage 485,465 565 1,220 2,336 4,121 489,586 Home equity 414,303 1,756 445 2,059 4,260 418,563 Installment and other consumer 65,111 352 73 31 456 65,567 Consumer construction 2,508 — — — — 2,508 Loans held for sale 2,970 — — — — 2,970 Total $ 3,850,597 $ 6,448 $ 2,214 $ 12,457 $ 21,119 $ 3,871,716
Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings	The following tables present the recorded investment in commercial loan classes by internally assigned risk ratings as of the dates presented: December 31, 2015 (dollars in thousands) Commercial Real Estate % of Total Commercial and Industrial % of Total Commercial Construction % of Total Total % of Total Pass $ 2,094,851 96.7 % $ 1,182,685 94.1 % $ 375,808 90.9 % $ 3,653,344 95.2 % Special mention 19,938 0.9 % 43,896 3.5 % 19,846 4.8 % 83,680 2.2 % Substandard 51,814 2.4 % 30,249 2.4 % 17,790 4.3 % 99,853 2.6 % Total $ 2,166,603 100.0 % $ 1,256,830 100.0 % $ 413,444 100.0 % $ 3,836,877 100.0 % December 31, 2014 (dollars in thousands) Commercial Real Estate % of Total Commercial and Industrial % of Total Commercial Construction % of Total Total % of Total Pass $ 1,635,132 97.2 % $ 948,663 95.4 % $ 196,520 90.9 % $ 2,780,315 96.1 % Special mention 23,597 1.4 % 30,357 3.1 % 12,014 5.6 % 65,968 2.3 % Substandard 23,507 1.4 % 15,118 1.5 % 7,614 3.5 % 46,239 1.6 % Total $ 1,682,236 100.0 % $ 994,138 100.0 % $ 216,148 100.0 % $ 2,892,522 100.0 %
Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status	The following tables present the recorded investment in consumer loan classes by performing and nonperforming status as of the dates presented: December 31, 2015 (dollars in thousands) Residential Mortgage % of Total Home Equity % of Total Installment and other consumer % of Total Consumer Construction % of Total Total % of Total Performing $ 633,743 99.1 % $ 467,943 99.4 % $ 73,839 99.8 % $ 6,579 100.0 % $ 1,182,104 99.3 % Nonperforming 5,629 0.9 % 2,902 0.6 % 100 0.2 % — — % 8,631 0.7 % Total $ 639,372 100.0 % $ 470,845 100.0 % $ 73,939 100.0 % $ 6,579 100.0 % $ 1,190,735 100.0 % December 31, 2014 (dollars in thousands) Residential Mortgage % of Total Home Equity % of Total Installment and other consumer % of Total Consumer Construction % of Total Total % of Total Performing $ 487,250 99.5 % $ 416,504 99.5 % $ 65,536 99.9 % $ 2,508 100.0 % $ 971,798 99.5 % Nonperforming 2,336 0.5 % 2,059 0.5 % 31 0.1 % — — % 4,426 0.5 % Total $ 489,586 100.0 % $ 418,563 100.0 % $ 65,567 100.0 % $ 2,508 100.0 % $ 976,224 100.0 %
Investments in Loans Considered to be Impaired and Related Information on Impaired Loans	The following table summarizes investments in loans considered to be impaired and related information on those impaired loans for the years presented: For the Year Ended December 31, 2015 December 31, 2014 (dollars in thousands) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized With a related allowance recorded: Commercial real estate $ — $ — $ — $ — Commercial and industrial — — — — Commercial construction 834 — — — Consumer real estate 120 7 48 4 Other consumer 2 — 24 2 Total with a Related Allowance Recorded 956 7 72 6 Without a related allowance recorded: Commercial real estate 14,622 597 20,504 684 Commercial and industrial 14,416 450 9,246 241 Commercial construction 10,581 329 8,145 227 Consumer real estate 6,902 364 7,027 396 Other consumer 117 1 56 2 Total without a Related Allowance Recorded 46,638 1,741 44,978 1,550 Total: Commercial real estate 14,622 597 20,504 684 Commercial and industrial 14,416 450 9,246 241 Commercial construction 11,415 329 8,145 227 Consumer real estate 7,022 371 7,075 400 Other consumer 119 1 80 4 Total $ 47,594 $ 1,748 $ 45,050 $ 1,556 The following tables summarize investments in loans considered to be impaired and related information on those impaired loans as of the dates presented: December 31, 2015 December 31, 2014 (dollars in thousands) Recorded Investment Unpaid Principal Balance Related Allowance Recorded Investment Unpaid Principal Balance Related Allowance With a related allowance recorded: Commercial real estate $ — $ — $ — $ — $ — $ — Commercial and industrial — — — — — — Commercial construction 500 1,350 3 — — — Consumer real estate 116 116 32 43 43 43 Other consumer 2 2 2 20 20 11 Total with a Related Allowance Recorded 618 1,468 37 63 63 54 Without a related allowance recorded: Commercial real estate 12,661 13,157 — 19,890 25,262 — Commercial and industrial 14,417 15,220 — 9,218 9,449 — Commercial construction 10,998 14,200 — 7,605 11,293 — Consumer real estate 6,845 7,521 — 7,159 7,733 — Other consumer 111 188 — 42 48 — Total without a Related Allowance Recorded 45,032 50,286 — 43,914 53,785 — Total: Commercial real estate 12,661 13,157 — 19,890 25,262 — Commercial and industrial 14,417 15,220 — 9,218 9,449 — Commercial construction 11,498 15,550 3 7,605 11,293 — Consumer real estate 6,961 7,637 32 7,202 7,776 43 Other consumer 113 190 2 62 68 11 Total $ 45,650 $ 51,754 $ 37 $ 43,977 $ 53,848 $ 54
Summary of Allowance for Loan Losses	The following tables detail activity in the ALL for the periods presented: 2015 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Consumer Real Estate Other Consumer Total Loans Balance at beginning of year $ 20,164 $ 13,668 $ 6,093 $ 6,333 $ 1,653 $ 47,911 Charge-offs (2,787 ) (5,463 ) (3,321 ) (2,167 ) (1,528 ) (15,266 ) Recoveries 3,545 605 143 495 326 5,114 Net Recoveries (Charge-offs) 758 (4,858 ) (3,178 ) (1,672 ) (1,202 ) (10,152 ) Provision for loan losses (5,879 ) 2,043 9,710 3,739 775 10,388 Balance at End of Year $ 15,043 $ 10,853 $ 12,625 $ 8,400 $ 1,226 $ 48,147 2014 (dollars in thousands) Commercial Real Estate Commercial and Industrial Commercial Construction Consumer Real Estate Other Consumer Total Loans Balance at beginning of year $ 18,921 $ 14,433 $ 5,374 $ 6,362 $ 1,165 $ 46,255 Charge-offs (2,041 ) (1,267 ) (712 ) (1,200 ) (1,133 ) (6,353 ) Recoveries 1,798 3,647 146 350 353 6,294 Net (Charge-offs)/ Recoveries (243 ) 2,380 (566 ) (850 ) (780 ) (59 ) Provision for loan losses 1,486 (3,145 ) 1,285 821 1,268 1,715 Balance at End of Year $ 20,164 $ 13,668 $ 6,093 $ 6,333 $ 1,653 $ 47,911
Summary of Allowance for Loan Losses and Recorded Investments	The following tables present the ALL and recorded investments in loans by category as of December 31: 2015 Allowance for Loan Losses Portfolio Loans (dollars in thousands) Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Commercial real estate $ — $ 15,043 $ 15,043 $ 12,661 $ 2,153,942 $ 2,166,603 Commercial and industrial — 10,853 10,853 14,417 1,242,413 1,256,830 Commercial construction 3 12,622 12,625 11,498 401,946 413,444 Consumer real estate 32 8,368 8,400 6,961 1,109,835 1,116,796 Other consumer 2 1,224 1,226 113 73,826 73,939 Total $ 37 $ 48,110 $ 48,147 $ 45,650 $ 4,981,962 $ 5,027,612 2014 Allowance for Loan Losses Portfolio Loans (dollars in thousands) Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Individually Evaluated for Impairment Collectively Evaluated for Impairment Total Commercial real estate $ — $ 20,164 $ 20,164 $ 19,890 $ 1,662,346 $ 1,682,236 Commercial and industrial — 13,668 13,668 9,218 984,920 994,138 Commercial construction — 6,093 6,093 7,605 208,543 216,148 Consumer real estate 43 6,290 6,333 7,202 903,455 910,657 Other consumer 11 1,642 1,653 62 65,505 65,567 Total $ 54 $ 47,857 $ 47,911 $ 43,977 $ 3,824,769 $ 3,868,746

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Summary of Premises and Equipment	The following table is a summary of premises and equipment as of the dates presented: December 31, (dollars in thousands) 2015 2014 Land $ 8,699 $ 6,193 Premises 52,968 44,690 Furniture and equipment 29,543 26,661 Leasehold improvements 7,186 6,545 98,396 84,089 Accumulated depreciation (49,269 ) (45,923 ) Total $ 49,127 $ 38,166
Minimum Annual Rental and Renewal Option Payments	Minimum annual rental and renewal option payments for each of the following five years and thereafter are approximately: (dollars in thousands) Operating Capital Total 2016 $ 2,860 $ 76 $ 2,936 2017 2,895 76 2,971 2018 2,899 76 2,975 2019 2,913 77 2,990 2020 2,857 77 2,934 Thereafter 53,107 610 53,717 Total $ 67,531 $ 992 $ 68,523

Goodwill and Other Intangible45

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	The following table presents goodwill as of the dates presented: December 31, (dollars in thousands) 2015 2014 Balance at beginning of year $ 175,820 $ 175,820 Additions 115,944 — Balance at End of Year $ 291,764 $ 175,820
Summary of Intangible Assets	The following table shows a summary of intangible assets as of the dates presented: December 31, (dollars in thousands) 2015 2014 Gross carrying amount at beginning of year $ 16,401 $ 16,401 Additions 5,713 — Accumulated amortization (15,589 ) (13,770 ) Balance at End of Year $ 6,525 $ 2,631
Summary of Expected Amortization Expense for Finite-Lived Intangibles Assets	The following is a summary of the expected amortization expense for finite-lived intangibles assets, assuming no new additions, for each of the five years following December 31, 2015: (dollars in thousands) Amount 2016 $ 1,433 2017 1,149 2018 668 2019 561 2020 475 Total $ 4,286

Derivative Instruments and He46

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Value of Derivative Assets and Derivative Liabilities	The following table indicates the amount representing the value of derivative assets and derivative liabilities at December 31: Derivatives (included in Other Assets) Derivatives (included in Other Liabilities) (dollars in thousands) 2015 2014 2015 2014 Derivatives not Designated as Hedging Instruments Interest Rate Swap Contracts—Commercial Loans Fair value $ 11,295 $ 12,981 $ 11,276 $ 12,953 Notional amount 245,595 245,152 245,595 245,152 Collateral posted — — 12,753 12,059 Interest Rate Lock Commitments—Mortgage Loans Fair value 261 235 — — Notional amount 9,894 8,822 — — Forward Sale Contracts—Mortgage Loans Fair value — — 5 57 Notional amount — — 9,800 7,789
Schedule of Gross Amounts of Derivative Assets and Derivative Liabilities	The following table indicates the gross amounts of commercial loan swap derivative assets and derivative liabilities, the amounts offset and the carrying values in the Consolidated Balance Sheets at December 31: Derivatives (included in Other Assets) Derivatives (included in Other Liabilities) (dollars in thousands) 2015 2014 2015 2014 Derivatives not Designated as Hedging Instruments Gross amounts recognized $ 11,295 $ 13,203 $ 11,276 $ 13,175 Gross amounts offset — (222 ) — (222 ) Net amounts presented in the Consolidated Balance Sheets 11,295 12,981 11,276 12,953 Gross amounts not offset (1) — — (12,573 ) (12,059 ) Net Amount $ 11,295 $ 12,981 $ (1,297 ) $ 894 (1) Amounts represent posted collateral.
Amount of Gain or Loss Recognized in Income on Derivatives	The following table indicates the gain or loss recognized in income on derivatives for the years ended December 31: (dollars in thousands) 2015 2014 2013 Derivatives not Designated as Hedging Instruments Interest rate swap contracts—commercial loans $ (8 ) $ (24 ) $ (174 ) Interest rate lock commitments—mortgage loans 26 150 (382 ) Forward sale contracts—mortgage loans 52 (90 ) 82 Total Derivative Gain (Loss) $ 70 $ 36 $ (474 )

Mortgage Servicing Rights (Tabl

Mortgage Servicing Rights (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of Mortgage Servicing Rights and Net Carrying Values	The following table indicates MSRs and the net carrying values: (dollars in thousands) Servicing Rights Valuation Allowance Net Carrying Value Balance at December 31, 2013 $ 3,208 $ (289 ) $ 2,919 Additions 431 — 431 Amortization (531 ) — (531 ) Temporary (impairment) recapture — (2 ) (2 ) Balance at December 31, 2014 $ 3,108 $ (291 ) $ 2,817 Additions 856 — 856 Amortization (538 ) — (538 ) Temporary (impairment) recapture — 102 102 Balance at December 31, 2015 $ 3,426 $ (189 ) $ 3,237

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Composition of Deposits and Interest Expenses	The following table presents the composition of deposits at December 31 and interest expense for the years ended December 31: 2015 2014 2013 (dollars in thousands) Balance Interest Expense Balance Interest Expense Balance Interest Expense Noninterest-bearing demand $ 1,227,766 $ — $ 1,083,919 $ — $ 992,779 $ — Interest-bearing demand 616,188 818 335,099 19 312,790 75 Money market 605,184 1,299 376,612 572 281,403 446 Savings 1,061,265 1,712 1,027,095 1,607 994,805 1,735 Certificates of deposit 1,366,208 9,115 1,086,117 7,930 1,090,531 9,150 Total $ 4,876,611 $ 12,944 $ 3,908,842 $ 10,128 $ 3,672,308 $ 11,406
Scheduled Maturities of Certificates of Deposit	The following table indicates the scheduled maturities of certificates of deposit at December 31, 2015: (dollars in thousands) Amount 2016 $ 870,679 2017 304,820 2018 102,886 2019 37,742 2020 41,808 Thereafter 8,273 Total $ 1,366,208

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Composition of Short-Term Borrowings, Interest Expense and Weighted Average Interest Rate	The following table represents the composition of short-term borrowings, the weighted average interest rate as of December 31 and interest expense for the years ended December 31: 2015 2014 2013 (dollars in thousands) Balance Weighted Average Interest Rate Interest Expense Balance Weighted Average Interest Rate Interest Expense Balance Weighted Average Interest Rate Interest Expense REPOs $ 62,086 0.01 % $ 4 $ 30,605 0.01 % $ 3 $ 33,847 0.01 % $ 62 FHLB advances 356,000 0.52 % 932 290,000 0.31 % 511 140,000 0.30 % 279 Total Short-term Borrowings $ 418,086 0.44 % $ 936 $ 320,605 0.27 % $ 514 $ 173,847 0.24 % $ 341

Long-Term Borrowings and Subo50

Long-Term Borrowings and Subordinated Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of Long-Term Borrowings, Interest Expense and Weighted Average Interest Rate	The following table represents the balance of long-term borrowings, the weighted average interest rate as of December 31 and interest expense for the years ended December 31: (dollars in thousand) 2015 2014 2013 Long-term borrowings $ 117,043 $ 19,442 $ 21,810 Weighted average interest rate 0.81 % 3.00 % 3.01 % Interest expense $ 790 $ 617 $ 746
Schedule of Annual Maturities and Average Interest Rate of Long-Term Debt	Scheduled annual maturities and average interest rates for all of our long-term debt, including a capital lease of $0.2 million , for each of the five years and thereafter subsequent to December 31, 2015 are as follows: (dollars in thousands) Balance Average Rate 2016 $ 102,330 0.52 % 2017 2,412 3.52 % 2018 2,496 3.60 % 2019 2,514 3.13 % 2020 2,004 3.22 % Thereafter 5,287 1.85 % Total $ 117,043 0.81 %
Schedule of Junior Subordinated Debt Securities and Interest Expense	The following table represents the composition of junior subordinated debt securities at December 31 and the interest expense for the years ended December 31: 2015 2014 2013 (dollars in thousands) Balance Interest Expense Balance Interest Expense Balance Interest Expense 2006 Junior subordinated debt $ 25,000 $ 554 $ 25,000 $ 463 $ 25,000 $ 475 2008 Junior subordinated debt—trust preferred securities 20,619 773 20,619 759 20,619 770 2008 Junior subordinated debt — — — — — 422 2008 Junior subordinated debt — — — — — 403 Total $ 45,619 $ 1,327 $ 45,619 $ 1,222 $ 45,619 $ 2,070
Schedule of Junior Subordinated Debt Securities	The following table summarizes the key terms of our junior subordinated debt securities: (dollars in thousands) 2006 Junior Subordinated Debt 2008 Trust Preferred Securities 2008 Junior Subordinated Debt 2008 Junior Subordinated Debt Junior Subordinated Debt $25,000 — $20,000 $25,000 Trust Preferred Securities — $20,619 — — Stated Maturity Date 12/15/2036 3/15/2038 6/15/2018 5/30/2018 Optional redemption date at par Any time after 9/15/2011 Any time after 3/15/2013 Any time after 6/15/2013 Any time after 5/30/2013 Regulatory Capital Tier 2 Tier 1 Tier 2 Tier 2 Interest Rate 3 month LIBOR plus 160 bps 3 month LIBOR plus 350 bps 3 month LIBOR plus 350 bps 3 month LIBOR plus 250 bps Interest Rate at December 31, 2015 2.11% 4.01% —% —%

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Letters of Credit	The following table sets forth our commitments and letters of credit as of the dates presented: December 31, (dollars in thousands) 2015 2014 Commitments to extend credit $ 1,619,854 $ 1,158,628 Standby letters of credit 97,676 73,584 Total $ 1,717,530 $ 1,232,212
Future Estimated Payments Related to Data Processing and Communication Charges	The following table sets forth the future estimated payments related to data processing and communication charges for each of the five years following December 31, 2015: (dollars in thousands) Total 2016 $ 11,360 2017 11,743 2018 12,123 2019 12,527 2020 12,951 Total $ 60,704

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Income Tax Expense (Benefit)	Income tax expense (benefit) for the years ended December 31 is comprised of: (dollars in thousands) 2015 2014 2013 Current $ 24,825 $ 15,979 $ 16,836 Deferred (427 ) 1,536 (2,358 ) Total $ 24,398 $ 17,515 $ 14,478
Schedule of Statutory to Effective Tax Rate Reconciliation	The statutory to effective tax rate reconciliation for the years ended December 31 is as follows: 2015 2014 2013 Statutory tax rate 35.0 % 35.0 % 35.0 % Low income housing tax credits (4.4 )% (5.8 )% (6.8 )% Tax-exempt interest (4.1 )% (4.6 )% (4.5 )% Bank owned life insurance (0.8 )% (0.8 )% (1.0 )% Other 1.0 % (0.6 )% (0.4 )% Effective Tax Rate 26.7 % 23.2 % 22.3 %
Schedule of Significant Components of Temporary Differences with Deferred Tax Assets and Liabilities	Significant components of our temporary differences were as follows at December 31: (dollars in thousands) 2015 2014 Deferred Tax Liabilities: Net unrealized holding gains on securities available-for-sale $ (3,563 ) $ (3,783 ) Prepaid pension (2,865 ) (3,472 ) Deferred loan income (2,847 ) (2,165 ) Purchase accounting adjustments — (631 ) Depreciation on premises and equipment (1,226 ) (1,590 ) Other (809 ) (812 ) Total Deferred Tax liabilities (11,310 ) (12,453 ) Deferred Tax Assets: Allowance for loan losses 17,740 17,567 Purchase accounting adjustments 1,298 — Other employee benefits 2,556 2,453 Low income housing partnerships 4,531 4,049 Net adjustment to funded status of pension 12,425 11,089 Impairment of securities 1,354 1,313 State net operating loss carryforwards 2,670 2,249 Other 6,155 4,668 Gross Deferred Tax Assets 48,729 43,388 Less: Valuation allowance (2,670 ) (2,249 ) Total Deferred Tax Assets 46,059 41,139 Net Deferred Tax Asset $ 34,749 $ 28,686
Schedule of Reconciliation of Change in Federal and State Gross Unrecognized Tax Benefits	The following table reconciles the change in Federal and State gross unrecognized tax benefits, or UTB, for the years ended December 31: (dollars in thousands) 2015 2014 2013 Balance at beginning of year $ 284 $ 1,902 $ 978 Prior period tax positions Increase 818 55 924 Decrease — (1,673 ) — Current period tax positions — — — Reductions for statute of limitations expirations — — — Balance at End of Year $ 1,102 $ 284 $ 1,902 Amount That Would Impact the Effective Tax Rate if Recognized $ 542 $ 184 $ 148

Tax Effects on Other Comprehe53

Tax Effects on Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Tax Effects of Components of Other Comprehensive Income (Loss)	The following tables present the tax effects of the components of other comprehensive income (loss) for the years ended December 31: (dollars in thousands) Pre-Tax Amount Tax (Expense) Benefit Net of Tax Amount 2015 Net change in unrealized gains on securities available-for-sale $ (663 ) $ 232 $ (431 ) Net available-for-sale securities losses reclassified into earnings 34 (12 ) 22 Adjustment to funded status of employee benefit plans (3,551 ) 1,336 (2,215 ) Other Comprehensive Income (Loss) $ (4,180 ) $ 1,556 $ (2,624 ) 2014 Net change in unrealized losses on securities available-for-sale $ 11,825 $ (4,139 ) $ 7,686 Net available-for-sale securities gains reclassified into earnings (41 ) 15 (26 ) Adjustment to funded status of employee benefit plans (13,394 ) 4,595 (8,799 ) Other Comprehensive Income (Loss) $ (1,610 ) $ 471 $ (1,139 ) 2013 Net change in unrealized gains on securities available-for-sale $ (16,928 ) $ 5,925 $ (11,003 ) Net available-for-sale securities gains reclassified into earnings (5 ) 2 (3 ) Adjustment to funded status of employee benefit plans 18,299 (6,405 ) 11,894 Other Comprehensive Income (Loss) $ 1,366 $ (478 ) $ 888

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Benefit Obligation and Plan Assets Deriving Funded Status, in Other Liabilities	The following table summarizes the activity in the benefit obligation and Plan assets deriving the funded status, which is recorded in other liabilities in the Consolidated Balance Sheets: (dollars in thousands) 2015 2014 Change in Projected Benefit Obligation Projected benefit obligation at beginning of year $ 113,124 $ 95,969 Service cost 2,601 2,369 Interest cost 4,425 4,470 Actuarial (gain) loss (4,257 ) 16,020 Benefits paid (6,146 ) (5,704 ) Projected Benefit Obligation at End of Year $ 109,747 $ 113,124 Change in Plan Assets Fair value of plan assets at beginning of year $ 93,486 $ 89,556 Actual return on plan assets (2,755 ) 9,634 Benefits paid (6,146 ) (5,704 ) Fair Value of Plan Assets at End of Year $ 84,585 $ 93,486 Funded Status $ (25,162 ) $ (19,638 )
Accumulated Other Comprehensive Income (Loss)	The following table sets forth the amounts recognized in accumulated other comprehensive income (loss) at December 31: (dollars in thousands) 2015 2014 Prior service credit $ (1,029 ) $ (1,167 ) Net actuarial loss 34,376 30,726 Total (Before Tax Effects) $ 33,347 $ 29,559
Actuarial Weighted Average Assumptions Used in Determining Benefit Obligation	Below are the actuarial weighted average assumptions used in determining the benefit obligation: 2015 2014 Discount rate 4.25 % 4.00 % Rate of compensation increase 3.00 % 3.00 %
Components of Net Periodic Pension Cost and Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Income (Loss)	The following table summarizes the components of net periodic pension cost and other changes in Plan assets and benefit obligations recognized in other comprehensive income (loss) for the years ended December 31: (dollars in thousands) 2015 2014 2013 Components of Net Periodic Pension Cost Service cost—benefits earned during the period $ 2,601 $ 2,369 $ 2,767 Interest cost on projected benefit obligation 4,425 4,470 3,985 Expected return on plan assets (7,180 ) (6,907 ) (6,207 ) Amortization of prior service credit (138 ) (137 ) (138 ) Recognized net actuarial loss 2,028 941 2,425 Net Periodic Pension Expense $ 1,736 $ 736 $ 2,832 Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Income (Loss) Net actuarial loss (gain) $ 5,678 $ 13,294 $ (15,499 ) Recognized net actuarial loss (2,028 ) (941 ) (2,425 ) Recognized prior service credit 138 137 138 Total (Before Tax Effects) $ 3,788 $ 12,490 $ (17,786 ) Total Recognized in Net Benefit Cost and Other Comprehensive Income (Loss) (Before Tax Effects) $ 5,524 $ 13,226 $ (14,954 )
Actuarial Weighted Average Assumptions Used in Determining Net Periodic Pension Cost	The following table summarizes the actuarial weighted average assumptions used in determining net periodic pension cost: 2015 2014 2013 Discount rate 4.00 % 4.75 % 4.00 % Rate of compensation increase 3.00 % 3.00 % 3.00 % Expected return on assets 8.00 % 8.00 % 8.00 %
Estimated Future Benefit Payments	The following table provides information regarding estimated future benefit payments to be paid in each of the next five years and in the aggregate for the five years thereafter: (dollars in thousands) Amount 2016 $ 6,455 2017 6,250 2018 6,643 2019 6,676 2020 7,298 2021 - 2025 38,488
Pension Plan Assets Measured at Fair Value on Recurring Basis	The following tables present our Plan assets measured at fair value on a recurring basis by fair value hierarchy level at December 31, 2015 and 2014. There were no transfers between Level 1 and Level 2 for items of a recurring basis during the periods presented. There were no purchases or transfers of Level 3 plan assets in 2015. December 31, 2015 Fair Value Asset Classes (1) (dollars in thousands) Level 1 Level 2 Level 3 Total Cash and cash equivalents (2) $ — $ 3,371 $ — $ 3,371 Fixed income (3) 27,054 — — 27,054 Equities: Equity index mutual funds—international (4) 3,421 — — 3,421 Domestic individual equities (5) 50,739 — — 50,739 Total Assets at Fair Value $ 81,214 $ 3,371 $ — $ 84,585 (1) Refer to Note 1 Summary of Significant Accounting Policies, Fair Value Measurements for a description of levels within the fair value hierarchy. (2) This asset class includes FDIC insured money market instruments. (3) This asset class includes a variety of fixed income mutual funds which primarily invest in investment grade rated securities. Investment managers have discretion to invest in fixed income related securities including futures, options and other derivatives. Investments may be made in currencies other than the U.S. dollar. (4) The sole investment within this asset class is the Harbor International Institutional Fund. (5) This asset class includes individual domestic equities invested in an active all-cap strategy. It may also include convertible bonds. December 31, 2014 Fair Value Asset Classes (1) (dollars in thousands) Level 1 Level 2 Level 3 Total Cash and cash equivalents (2) $ — $ 5,073 $ — $ 5,073 Fixed income (3) 26,726 — — 26,726 Equities: Equity index mutual funds—international (4) 3,728 — — 3,728 Domestic individual equities (5) 57,085 — — 57,085 International individual equities (6) 874 — — 874 Total Assets at Fair Value $ 88,413 $ 5,073 $ — $ 93,486 (1) Refer to Note 1 Summary of Significant Accounting Policies, Fair Value Measurements for a description of levels within the fair value hierarchy. (2) This asset class includes FDIC insured money market instruments. (3) This asset class includes a variety of fixed income mutual funds which primarily invest in investment grade rated securities. Investment managers have discretion to invest in fixed income related securities including futures, options and other derivatives. Investments may be made in currencies other than the U.S. dollar. (4) The sole investment within this asset class is MSCI EAFE Index iShares. (5) This asset class includes individual domestic equities invested in an active all-cap strategy. It may also include convertible bonds. (6) This asset class includes American Depository Receipts.

Incentive and Restricted Stoc55

Incentive and Restricted Stock Plan and Dividend Reinvestment Plan (Tables)	12 Months Ended
	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Nonstatutory Stock Options Activity	The following table summarizes activity for nonstatutory stock options for the years ended December 31: 2015 2014 2013 Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at beginning of year 155,500 $ 37.86 428,900 $ 37.36 675,500 $ 35.18 Granted — — — — — — Exercised — — — — — — Forfeited — — (273,400 ) 37.08 (246,600 ) 31.39 Expired (155,500 ) 37.86 — — — — Outstanding at End of Year — — 0.0 years 155,500 $ 37.86 1.0 year 428,900 $ 37.36 1.4 years Exercisable at End of Year — — 0.0 years 155,500 $ 37.86 1.0 year 428,900 $ 37.36 1.4 years
2003 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Non-Vested Restricted Stock	The following table provides information about restricted stock granted under the 2003 Stock Plan for the years ended December 31: Restricted Stock Weighted Average Grant Date Fair Value Non-vested at December 31, 2013 79,415 $ 21.50 Granted — — Vested 41,740 20.70 Forfeited 14,530 20.97 Non-vested at December 31, 2014 23,145 $ 23.28 Granted — — Vested 15,433 22.34 Forfeited 7,712 22.34 Non-vested at December 31, 2015 — $ —
2014 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Non-Vested Restricted Stock	The following table provides information about restricted stock granted under the 2014 Stock Plan for the years ended December 31: Restricted Stock Weighted Average Grant Date Fair Value Non-vested at December 31, 2013 — $ — Granted 80,455 23.24 Vested 158 23.19 Forfeited 473 23.19 Non-vested at December 31, 2014 79,824 $ 23.24 Granted 87,841 28.71 Vested 14,126 23.57 Forfeited 3,183 26.15 Non-vested at December 31, 2015 150,356 $ 26.34

Parent Company Condensed Fina56

Parent Company Condensed Financial Information (Tables)	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Balance Sheets	BALANCE SHEETS December 31, (dollars in thousands) 2015 2014 ASSETS Cash $ 12,595 $ 38,028 Investments in: Bank subsidiary 777,795 565,927 Nonbank subsidiaries 20,624 20,569 Other assets 2,530 5,567 Total Assets $ 813,544 $ 630,091 LIABILITIES Long-term debt $ 20,619 $ 20,619 Other liabilities 688 1,083 Total Liabilities 21,307 21,702 Total Shareholders’ Equity 792,237 608,389 Total Liabilities and Shareholders’ Equity $ 813,544 $ 630,091
Statements of Net Income	STATEMENTS OF NET INCOME Years ended December 31, (dollars in thousands) 2015 2014 2013 Dividends from subsidiaries $ 75,413 $ 46,414 $ 24,087 Investment income 19 19 15 Interest expense on long-term debt 773 759 769 Other expenses 2,138 2,014 2,579 Income before Equity in Undistributed Net Income of Subsidiaries 72,521 43,660 20,754 Equity in undistributed net income (distribution in excess of net income) of: Bank subsidiary (5,064 ) 13,351 29,926 Nonbank subsidiaries (376 ) 899 (141 ) Net Income $ 67,081 $ 57,910 $ 50,539
Statements of Cash Flows	STATEMENTS OF CASH FLOWS Years ended December 31, (dollars in thousands) 2015 2014 2013 OPERATING ACTIVITIES Net Income $ 67,081 $ 57,910 $ 50,539 Equity in undistributed (earnings) losses of subsidiaries 5,440 (14,250 ) (29,785 ) Tax benefit from stock-based compensation (53 ) (16 ) (96 ) Other 3,059 (106 ) 121 Net Cash Provided by Operating Activities 75,527 43,538 20,779 INVESTING ACTIVITIES Net investments in subsidiaries (38,404 ) — — Acquisitions (29,510 ) — — Net Cash Used in Investing Activities (67,914 ) — — FINANCING ACTIVITIES Repayment of junior subordinated debt (8,500 ) — — (Purchase) Sale of treasury shares, net (112 ) (163 ) (88 ) Cash dividends paid to common shareholders (24,487 ) (20,215 ) (18,137 ) Tax benefit from stock-based compensation 53 16 96 Net Cash Used in Financing Activities (33,046 ) (20,362 ) (18,129 ) Net increase (decrease) in cash (25,433 ) 23,176 2,650 Cash at beginning of year 38,028 14,852 12,202 Cash at End of Year $ 12,595 $ 38,028 $ 14,852

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Summary of Risk-Based Capital Amounts and Ratios	The following table summarizes risk-based capital amounts and ratios for S&T and S&T Bank: Actual Minimum Regulatory Capital Requirements To be Well Capitalized Under Prompt Corrective Action Provisions (dollars in thousands) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2015 Leverage Ratio S&T $ 535,234 8.96 % $ 238,841 4.00 % $ 298,551 5.00 % S&T Bank 502,114 8.43 % 238,121 4.00 % 297,651 5.00 % Common Equity Tier 1 (to Risk-Weighted Assets) S&T 515,234 9.77 % 237,315 4.50 % 342,788 6.50 % S&T Bank 502,114 9.55 % 236,482 4.50 % 341,584 6.50 % Tier 1 Capital (to Risk-Weighted Assets) S&T 535,234 10.15 % 316,419 6.00 % 421,892 8.00 % S&T Bank 502,114 9.55 % 315,309 6.00 % 420,412 8.00 % Total Capital (to Risk-Weighted Assets) S&T 611,859 11.60 % 421,892 8.00 % 527,366 10.00 % S&T Bank 577,824 11.00 % 420,412 8.00 % 525,515 10.00 % As of December 31, 2014 Leverage Ratio (1) S&T $ 465,114 9.80 % $ 189,895 4.00 % $ 237,369 5.00 % S&T Bank 403,593 8.53 % 189,182 4.00 % 236,477 5.00 % Common Equity Tier 1 (to Risk-Weighted Assets) S&T 445,114 11.81 % 169,621 4.50 % 245,008 6.50 % S&T Bank 403,593 10.76 % 168,804 4.50 % 243,827 6.50 % Tier 1 Capital (to Risk-Weighted Assets) S&T 465,114 12.34 % 150,774 4.00 % 226,161 6.00 % S&T Bank 403,593 10.76 % 150,048 4.00 % 225,071 6.00 % Total Capital (to Risk-Weighted Assets) S&T 537,935 14.27 % 301,548 8.00 % 376,936 10.00 % S&T Bank 475,538 12.68 % 300,095 8.00 % 375,119 10.00 %

Segments (Tables)

Segments (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Total Assets by Reportable Operating Segment	The following represents total assets by reportable operating segment as of December 31: (dollars in thousands) 2015 2014 Community Banking $ 6,305,046 $ 4,954,728 Insurance 9,619 7,468 Wealth Management 3,689 2,490 Total Assets $ 6,318,354 $ 4,964,686
Financial Information of Segments	For the Year Ended December 31, 2015 (dollars in thousands) Community Banking Insurance Wealth Management Eliminations Consolidated Interest income $ 203,439 $ 2 $ 508 $ (401 ) $ 203,548 Interest expense 16,678 — — (681 ) 15,997 Net interest income 186,761 2 508 280 187,551 Provision for loan losses 10,388 — — — 10,388 Noninterest income 34,106 5,035 11,412 480 51,033 Noninterest expense 115,998 4,365 9,037 760 130,160 Depreciation expense 4,664 50 25 — 4,739 Amortization of intangible assets 1,738 50 30 — 1,818 Provision for income taxes 23,209 200 989 — 24,398 Net Income $ 64,870 $ 372 $ 1,839 $ — $ 67,081 For the Year Ended December 31, 2014 (dollars in thousands) Community Banking Insurance Wealth Management Eliminations Consolidated Interest income $ 160,403 $ 2 $ 518 $ (400 ) $ 160,523 Interest expense 13,989 — — (1,508 ) 12,481 Net interest income 146,414 2 518 1,108 148,042 Provision for loan losses 1,715 — — — 1,715 Noninterest income 29,443 5,279 11,297 319 46,338 Noninterest expense 97,733 4,313 9,173 1,427 112,646 Depreciation expense 3,387 51 27 — 3,465 Amortization of intangible assets 1,039 51 39 — 1,129 Provision for income taxes 16,311 303 901 — 17,515 Net Income $ 55,672 $ 563 $ 1,675 $ — $ 57,910 For the Year Ended December 31, 2013 (dollars in thousands) Community Banking Insurance Wealth Management Eliminations Consolidated Interest income $ 153,450 $ 2 $ 517 $ (213 ) $ 153,756 Interest expense 16,508 — — (1,945 ) 14,563 Net interest income 136,942 2 517 1,732 139,193 Provision for loan losses 8,311 — — — 8,311 Noninterest income 34,649 5,483 10,662 733 51,527 Noninterest expense 94,769 5,210 9,850 2,465 112,294 Depreciation expense 3,430 47 30 — 3,507 Amortization of intangible assets 1,492 51 48 — 1,591 Provision (benefit) for income taxes 14,180 (47 ) 345 — 14,478 Net Income $ 49,409 $ 224 $ 906 $ — $ 50,539

Selected Financial Data (Tables

Selected Financial Data (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Selected Financial Data	The following table presents selected financial data for the most recent eight quarters. 2015 2014 (dollars in thousands, except per share data) (unaudited) Fourth Quarter Third Quarter Second Quarter First Quarter Fourth Quarter Third Quarter Second Quarter First Quarter SUMMARY OF OPERATIONS Interest income $ 53,353 $ 53,669 $ 52,611 $ 43,916 $ 41,381 $ 40,605 $ 39,872 $ 38,665 Interest expense 4,468 4,073 3,800 3,657 3,315 3,076 3,017 3,074 Provision for loan losses 3,915 3,206 2,059 1,207 1,106 1,454 (1,134 ) 289 Net Interest Income After Provision For Loan Losses 44,970 46,390 46,752 39,052 36,960 36,075 37,989 35,302 Security (losses) gains, net — — (34 ) — — — 40 1 Noninterest income 13,084 12,481 13,417 12,084 11,220 11,931 11,731 11,415 Noninterest expense 33,817 33,829 35,449 33,621 29,720 28,440 30,165 28,914 Income Before Taxes 24,237 25,042 24,686 17,515 18,460 19,566 19,595 17,804 Provision for income taxes 6,814 6,407 6,498 4,680 3,963 4,906 4,875 3,771 Net Income Available to Common Shareholders $ 17,423 $ 18,635 $ 18,188 $ 12,835 $ 14,497 $ 14,660 $ 14,720 $ 14,033 Per Share Data Common earnings per share—diluted $ 0.50 $ 0.54 $ 0.52 $ 0.41 $ 0.49 $ 0.49 $ 0.49 $ 0.47 Dividends declared per common share 0.19 0.18 0.18 0.18 0.18 0.17 0.17 0.16 Common book value 22.76 22.63 22.15 21.91 20.42 20.33 20.04 19.64

Summary of Significant Accoun60

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)segmententitysubsidiary	Mar. 04, 2015USD ($)	Dec. 31, 2014USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of subsidiary | subsidiary	3
Percentage of outstanding common stock of investees accounted for using equity method of accounting	100.00%
Number of entities non-banking activities | entity	5
Assets	$ 6,318,354		$ 4,964,686
Period for satisfactory payment of TDRs	6 months
Evaluation for impairment of substandard and nonaccrual commercial loans	$ 500
Number of reporting units | segment	3
Goodwill	$ 291,764		175,820
Amortization period of intangible assets	10 years
Percentage of amount recognized of tax benefit	50.00%
Community Banking
Summary Of Significant Accounting Policies [Line Items]
Assets	$ 6,305,046		4,954,728
Goodwill	$ 287,600
Percentage of goodwill to reporting units	99.00%
Insurance
Summary Of Significant Accounting Policies [Line Items]
Assets	$ 9,619		$ 7,468
Goodwill	$ 4,200
Percentage of goodwill to reporting units	1.00%
Interest Rate Lock Commitments
Summary Of Significant Accounting Policies [Line Items]
Period for interest rate lock commitment	60 days
Integrity Bancshares, Inc.
Summary Of Significant Accounting Policies [Line Items]
Goodwill	$ 115,944	$ 115,900
Common Wealth Trust Life Insurance Company
Summary Of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	50.00%
Minimum
Summary Of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	20.00%
Maximum
Summary Of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	50.00%
Core Deposits And Customers Lists | Minimum
Summary Of Significant Accounting Policies [Line Items]
Acquired finite-lived intangibles, weighted average life	10 years
Core Deposits And Customers Lists | Maximum
Summary Of Significant Accounting Policies [Line Items]
Acquired finite-lived intangibles, weighted average life	20 years
Corporate Joint Venture [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	50.00%

Summary of Significant Accoun61

Summary of Significant Accounting Policies - Estimated Useful Lives for Various Asset (Detail)	12 Months Ended
	Dec. 31, 2015
Land and Land Improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives, description	Non-depreciating assets
Buildings
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	25 years
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	5 years
Computer Equipment and Software
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	5 years
Other Equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	5 years
Vehicles
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	5 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	15 years

Business Combinations Additiona

Business Combinations Additional Information (Details) - USD ($)	Mar. 04, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill		$ 291,764,000	$ 291,764,000	$ 175,820,000
Merger Related Expenses			3,167,000	689,000	$ 838,000
Data Processing, Contract Termination and Conversion Cost Expenses			1,300,000	0	800,000
Professional Services and Legal			3,365,000	$ 3,717,000	$ 4,184,000
Integrity Bancshares, Inc.
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%
Cash per share offered in exchange	$ 52.50
Shares of S&T Offered for Each Share of Integrity (shares)	2.0627
Fair value of consideration	$ 172,000,000		171,979,000
Cash	$ 29,500,000		29,510,000
S&T Common Shares Issued (shares)	4,933,115
S&T Common Shares Issued, Fair Value (in USD per Share)	$ 28.88
Purchase accounting adjustments, increase to goodwill		1,100,000
Purchase accounting adjustment, decrease to land		800,000
Purchase accounting adjustment, Decrease to deferred tax assets		300,000
Goodwill	$ 115,900,000	115,944,000	115,944,000
Carryover of Allowance for Loan Losses	0	0	0
Acquired loans	788,700,000	$ 788,687,000	788,687,000
Discount on Loans Acquired	14,800,000
Merger Related Expenses			3,200,000
Data Processing, Contract Termination and Conversion Cost Expenses			1,300,000
Professional Services and Legal			1,200,000
Severance Payments			400,000
Other Expenses			$ 300,000
Integrity Bancshares, Inc. | Commercial Real Estate
Business Acquisition [Line Items]
Acquired loans	331,600,000
Integrity Bancshares, Inc. | Residential Mortgage
Business Acquisition [Line Items]
Acquired loans	116,900,000
Integrity Bancshares, Inc. | Home Equity
Business Acquisition [Line Items]
Acquired loans	25,600,000
Integrity Bancshares, Inc. | Installment and Other Consumer
Business Acquisition [Line Items]
Acquired loans	36,100,000
Integrity Bancshares, Inc. | Consumer Construction
Business Acquisition [Line Items]
Acquired loans	1,900,000
Integrity Bancshares, Inc. | Commercial and Industrial
Business Acquisition [Line Items]
Acquired loans	$ 184,200,000

Business Combinations Considera

Business Combinations Consideration, Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 04, 2015	Dec. 31, 2015	Dec. 31, 2014
Fair Value of Liabilities Assumed
Goodwill		$ 291,764	$ 175,820
Integrity Bancshares, Inc.
Business Acquisition [Line Items]
Cash	$ 29,500	29,510
Common stock		142,469
Fair Value of Total Consideration	172,000	171,979
Fair Value of Assets Acquired
Cash and cash equivalents		13,163
Securities and other investments		11,502
Loans	788,700	788,687
Bank owned life insurance		15,974
Premises and equipment		10,855
Core deposit intangible		5,713
Other assets		18,994
Total Assets Acquired		864,888
Fair Value of Liabilities Assumed
Deposits		722,308
Borrowings		82,286
Other liabilities		4,259
Total Liabilities Assumed		808,853
Total Fair Value of Identifiable Net Assets		56,035
Goodwill	$ 115,900	$ 115,944

Business Combinations Pro Forma

Business Combinations Pro Forma Information (Details) - Integrity Bancshares, Inc. - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition, Pro Forma Information [Abstract]
Total revenue	$ 240,581	$ 232,635
Net income	$ 68,850	$ 70,001
Earnings per common share
Basic (in USD per share)	$ 1.78	$ 2.02
Diluted (in USD per share)	$ 1.77	$ 2.02

Earnings Per Share - Reconciles

Earnings Per Share - Reconciles Numerators and Denominators of Basic Earnings Per Share and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator for Earnings per Common Share-Basic:
Net Income									$ 67,081	$ 57,910	$ 50,539
Less: Income allocated to participating shares									280	165	147
Net Income Available to Common Shareholders	$ 17,423	$ 18,635	$ 18,188	$ 12,835	$ 14,497	$ 14,660	$ 14,720	$ 14,033	66,801	57,745	50,392
Numerator for Earnings per Common Share-Diluted:
Net Income									$ 67,081	$ 57,910	$ 50,539
Denominators:
Weighted Average Common Shares Outstanding-Basic (in shares)									33,812,990	29,683,103	29,647,231
Add: Dilutive potential common shares (in shares)									35,092	25,621	35,322
Denominator for Treasury Stock Method-Diluted (in shares)									33,848,082	29,708,724	29,682,553
Weighted Average Common Shares Outstanding-Basic (in shares)									33,812,990	29,683,103	29,647,231
Add: Average participating shares outstanding (in shares)									141,558	84,918	86,490
Denominator for Two-Class Method-Diluted									33,954,548	29,768,021	29,733,721
Earnings per common share—basic (in USD per share)									$ 1.98	$ 1.95	$ 1.70
Earnings per common share—diluted (in USD per share)	$ 0.50	$ 0.54	$ 0.52	$ 0.41	$ 0.49	$ 0.49	$ 0.49	$ 0.47	1.98	$ 1.95	$ 1.70
Exercise price of warrants (dollars per share)	$ 31.53								$ 31.53
Warrants
Denominators:
Anti-dilutive excluded from dilutive potential common shares (in shares)									517,012	517,012	517,012
Stock Options
Denominators:
Anti-dilutive excluded from dilutive potential common shares (in shares)									0	419,538	619,418
Restricted Stock
Denominators:
Anti-dilutive excluded from dilutive potential common shares (in shares)									106,466	59,297	51,169

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Loans Receivable [Line Items]
Level 1 to Level 2 transfers	$ 0	$ 0
Level 2 to Level 1 transfers	0	0
Level 1 to Level 2 transfers	0	0
evel 2 to Level 1 transfers	0	0
Liabilities measured at fair value on nonrecurring basis	$ 0	0
Level 3
Loans Receivable [Line Items]
Liabilities measured at fair value on a recurring basis		$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Securities available-for-sale, at fair value	$ 660,963,000	$ 640,273,000
U.S. Treasury securities
ASSETS
Securities available-for-sale, at fair value	14,941,000	14,880,000
Obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	263,303,000	269,285,000
Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	128,835,000	118,006,000
Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	40,125,000	46,668,000
Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	69,204,000	39,673,000
Obligations of states and political subdivisions
ASSETS
Securities available-for-sale, at fair value	134,886,000	142,702,000
Marketable equity securities
ASSETS
Securities available-for-sale, at fair value	9,669,000	9,059,000
Level 3
LIABILITIES
Total Liabilities		0
Fair Value Measurements, Recurring
ASSETS
Securities available-for-sale, at fair value	660,963,000	640,273,000
Trading securities held in a Rabbi Trust	4,021,000	3,456,000
Total securities	664,984,000	643,729,000
Total Assets	676,540,000	656,945,000
LIABILITIES
Total Liabilities	11,281,000	13,010,000
Fair Value Measurements, Recurring | U.S. Treasury securities
ASSETS
Securities available-for-sale, at fair value	14,941,000	14,880,000
Fair Value Measurements, Recurring | Obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	263,303,000	269,285,000
Fair Value Measurements, Recurring | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	128,835,000	118,006,000
Fair Value Measurements, Recurring | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	40,125,000	46,668,000
Fair Value Measurements, Recurring | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	69,204,000	39,673,000
Fair Value Measurements, Recurring | Obligations of states and political subdivisions
ASSETS
Securities available-for-sale, at fair value	134,886,000	142,702,000
Fair Value Measurements, Recurring | Marketable equity securities
ASSETS
Securities available-for-sale, at fair value	9,669,000	9,059,000
Fair Value Measurements, Recurring | Interest Rate Swap
ASSETS
Derivative financial assets	11,295,000	12,981,000
LIABILITIES
Derivative financial liabilities	11,276,000	12,953,000
Fair Value Measurements, Recurring | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	261,000	235,000
Fair Value Measurements, Recurring | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	5,000	57,000
Fair Value Measurements, Recurring | Level 1
ASSETS
Securities available-for-sale, at fair value		178,000
Trading securities held in a Rabbi Trust	4,021,000	3,456,000
Total securities	4,021,000	3,634,000
Total Assets	4,021,000	3,634,000
Fair Value Measurements, Recurring | Level 1 | U.S. Treasury securities
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 1 | Obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 1 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 1 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 1 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 1 | Obligations of states and political subdivisions
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 1 | Marketable equity securities
ASSETS
Securities available-for-sale, at fair value	0	178,000
Fair Value Measurements, Recurring | Level 1 | Interest Rate Swap
ASSETS
Derivative financial assets	0	0
LIABILITIES
Derivative financial liabilities	0	0
Fair Value Measurements, Recurring | Level 1 | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	0	0
Fair Value Measurements, Recurring | Level 1 | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	0	0
Fair Value Measurements, Recurring | Level 2
ASSETS
Securities available-for-sale, at fair value	660,963,000	640,095,000
Trading securities held in a Rabbi Trust	0	0
Total securities	660,963,000	640,095,000
Total Assets	672,519,000	653,311,000
LIABILITIES
Total Liabilities	11,281,000	13,010,000
Fair Value Measurements, Recurring | Level 2 | U.S. Treasury securities
ASSETS
Securities available-for-sale, at fair value	14,941,000	14,880,000
Fair Value Measurements, Recurring | Level 2 | Obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	263,303,000	269,285,000
Fair Value Measurements, Recurring | Level 2 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	128,835,000	118,006,000
Fair Value Measurements, Recurring | Level 2 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	40,125,000	46,668,000
Fair Value Measurements, Recurring | Level 2 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	69,204,000	39,673,000
Fair Value Measurements, Recurring | Level 2 | Obligations of states and political subdivisions
ASSETS
Securities available-for-sale, at fair value	134,886,000	142,702,000
Fair Value Measurements, Recurring | Level 2 | Marketable equity securities
ASSETS
Securities available-for-sale, at fair value	9,669,000	8,881,000
Fair Value Measurements, Recurring | Level 2 | Interest Rate Swap
ASSETS
Derivative financial assets	11,295,000	12,981,000
LIABILITIES
Derivative financial liabilities	11,276,000	12,953,000
Fair Value Measurements, Recurring | Level 2 | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	261,000	235,000
Fair Value Measurements, Recurring | Level 2 | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	5,000	57,000
Fair Value Measurements, Recurring | Level 3
ASSETS
Trading securities held in a Rabbi Trust	0	0
Fair Value Measurements, Recurring | Level 3 | U.S. Treasury securities
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 3 | Obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 3 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 3 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 3 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 3 | Obligations of states and political subdivisions
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 3 | Marketable equity securities
ASSETS
Securities available-for-sale, at fair value	0	0
Fair Value Measurements, Recurring | Level 3 | Interest Rate Swap
ASSETS
Derivative financial assets	0	0
LIABILITIES
Derivative financial liabilities	0	0
Fair Value Measurements, Recurring | Level 3 | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	0	$ 0
Fair Value Measurements, Recurring | Level 3 | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	$ 0

Fair Value Measurements - Ass68

Fair Value Measurements - Assets Measured at Estimated Fair Value on Nonrecurring Basis by Fair Value Hierarchy (Detail) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Impaired loans	$ 9,373	$ 12,916
Other real estate owned	158	117
Mortgage servicing rights	3,396	2,934
Total Assets	12,927	15,967
Level 1
ASSETS
Impaired loans	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Level 2
ASSETS
Impaired loans	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Level 3
ASSETS
Impaired loans	9,373	12,916
Other real estate owned	158	117
Mortgage servicing rights	3,396	2,934
Total Assets	$ 12,927	$ 15,967

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Securities available-for-sale, at fair value	$ 660,963	$ 640,273
FHLB and other restricted stock	23,032	15,135
LIABILITIES
Junior subordinated debt securities	45,619	45,619	$ 45,619
Carrying Value
ASSETS
Cash and due from banks, including interest-bearing deposits	99,399	109,580
Securities available-for-sale, at fair value	660,963	640,273
Loans held for sale	35,321	2,970
Portfolio loans, net of unearned income	5,027,612	3,868,746
Bank owned life insurance	70,175	62,252
FHLB and other restricted stock	23,032	15,135
Trading securities held in a Rabbi Trust	4,021	3,456
Mortgage servicing rights	3,237	2,817
LIABILITIES
Deposits	4,876,611	3,908,842
Securities sold under repurchase agreements	62,086	30,605
Short-term borrowings	356,000	290,000
Long-term borrowings	117,043	19,442
Junior subordinated debt securities	45,619	45,619
Carrying Value | Interest Rate Swap
ASSETS
Derivative financial assets	11,295	12,981
LIABILITIES
Derivative financial liabilities	11,276	12,953
Carrying Value | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	261	235
Carrying Value | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	5	57
Fair Value Measurements
ASSETS
Cash and due from banks, including interest-bearing deposits	99,399	109,580
Securities available-for-sale, at fair value	660,963	640,273
Loans held for sale	35,500	2,991
Portfolio loans, net of unearned income	5,001,004	3,827,634
Bank owned life insurance	70,175	62,252
FHLB and other restricted stock	23,032	15,135
Trading securities held in a Rabbi Trust	4,021	3,456
Mortgage servicing rights	3,396	2,934
LIABILITIES
Deposits	4,881,718	3,910,342
Securities sold under repurchase agreements	62,086	30,605
Short-term borrowings	356,000	290,000
Long-term borrowings	117,859	20,462
Junior subordinated debt securities	45,619	45,619
Fair Value Measurements | Level 1
ASSETS
Cash and due from banks, including interest-bearing deposits	99,399	109,580
Securities available-for-sale, at fair value		178
Trading securities held in a Rabbi Trust	4,021	3,456
Fair Value Measurements | Level 2
ASSETS
Securities available-for-sale, at fair value	660,963	640,095
Bank owned life insurance	70,175	62,252
Fair Value Measurements | Level 3
ASSETS
Loans held for sale	35,500	2,991
Portfolio loans, net of unearned income	5,001,004	3,827,634
FHLB and other restricted stock	23,032	15,135
Mortgage servicing rights	3,396	2,934
LIABILITIES
Deposits	4,881,718	3,910,342
Securities sold under repurchase agreements	62,086	30,605
Short-term borrowings	356,000	290,000
Long-term borrowings	117,859	20,462
Junior subordinated debt securities	45,619	45,619
Fair Value Measurements | Interest Rate Swap
ASSETS
Derivative financial assets	11,295	12,981
LIABILITIES
Derivative financial liabilities	11,276	12,953
Fair Value Measurements | Interest Rate Swap | Level 2
ASSETS
Derivative financial assets	11,295	12,981
LIABILITIES
Derivative financial liabilities	11,276	12,953
Fair Value Measurements | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	261	235
Fair Value Measurements | Interest Rate Lock Commitments | Level 2
ASSETS
Derivative financial assets	261	235
Fair Value Measurements | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	5	57
Fair Value Measurements | Forward Sale Contracts | Level 2
LIABILITIES
Derivative financial liabilities	$ 5	$ 57

Restrictions on Cash and Due 70

Restrictions on Cash and Due from Bank Accounts - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Abstract]
Restricted Cash and Cash Equivalents, Current	$ 44.1
Restricted Cash and Cash Equivalents		$ 41.8	$ 39.7

Dividend and Loan Restrictions

Dividend and Loan Restrictions - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Percentage of collateralized loans	10.00%

Securities Available-for-Sale -

Securities Available-for-Sale - Composition of Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 650,782	$ 629,463
Gross Unrealized Gains	11,897	12,647
Gross Unrealized Losses	(1,716)	(1,837)
Fair Value	660,963	640,273
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,914	14,873
Gross Unrealized Gains	27	7
Gross Unrealized Losses	0	0
Fair Value	14,941	14,880
Obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	262,045	268,029
Gross Unrealized Gains	1,825	2,334
Gross Unrealized Losses	(567)	(1,078)
Fair Value	263,303	269,285
Collateralized mortgage obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	128,458	116,897
Gross Unrealized Gains	693	1,257
Gross Unrealized Losses	(316)	(148)
Fair Value	128,835	118,006
Residential mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	39,185	45,274
Gross Unrealized Gains	1,091	1,548
Gross Unrealized Losses	(151)	(154)
Fair Value	40,125	46,668
Commercial mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	69,697	39,834
Gross Unrealized Gains	183	232
Gross Unrealized Losses	(676)	(393)
Fair Value	69,204	39,673
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	128,904	136,977
Gross Unrealized Gains	5,988	5,789
Gross Unrealized Losses	(6)	(64)
Fair Value	134,886	142,702
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	643,203	621,884
Gross Unrealized Gains	9,807	11,167
Gross Unrealized Losses	(1,716)	(1,837)
Fair Value	651,294	631,214
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,579	7,579
Gross Unrealized Gains	2,090	1,480
Gross Unrealized Losses	0	0
Fair Value	$ 9,669	$ 9,059

Securities Available-for-Sale73

Securities Available-for-Sale - Schedule of Gross and Net Realized Gains and Losses on Sale of Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 0	$ 41	$ 5
Gross realized losses	(34)	0	0
Net Realized Gains	$ (34)	$ 41	$ 5

Securities Available-for-Sale74

Securities Available-for-Sale - Fair Value and Age of Gross Unrealized Losses by Investment Category (Detail) $ in Thousands	Dec. 31, 2015USD ($)security	Dec. 31, 2014USD ($)security
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	23	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 213,997	$ 59,329
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (1,302)	$ (381)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	3	13
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 24,014	$ 103,527
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ (414)	$ (1,456)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	26	20
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 238,011	$ 162,856
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (1,716)	$ (1,837)
Obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	10	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 88,584	$ 39,745
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (379)	$ (207)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	2	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 14,542	$ 63,149
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ (188)	$ (871)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	12	12
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 103,126	$ 102,894
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (567)	$ (1,078)
Collateralized mortgage obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	6	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 61,211	$ 9,323
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (316)	$ (148)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	6	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 61,211	$ 9,323
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (316)	$ (148)
Residential mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	1	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 7,993	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (151)	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 8,982
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ (154)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 7,993	$ 8,982
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (151)	$ (154)
Commercial mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	5	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 50,839	$ 9,998
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (450)	$ (25)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	1	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 9,472	$ 20,640
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ (226)	$ (368)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	6	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 60,311	$ 30,638
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (676)	$ (393)
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 5,370	$ 263
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (6)	$ (1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 10,756
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ (63)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	1	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 5,370	$ 11,019
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (6)	$ (64)

Securities Available-for-Sale75

Securities Available-for-Sale - Additional Information (Detail)	Dec. 31, 2015USD ($)security	Dec. 31, 2014USD ($)
Schedule of Available-for-sale Securities [Line Items]
Number of debt securities on which unrealized losses were primarily attributable to changes in interest | security	26
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,716,000	$ 1,837,000
Carrying values of securities	278,400,000	289,100,000
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 0	$ 0

Securities Available-for-Sale76

Securities Available-for-Sale - Unrealized Gains (Losses) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Total unrealized gains/(losses) on securities available for sale, Gross Unrealized Gains	$ 11,897	$ 12,647
Total unrealized gains/(losses) on securities available for sale, Gross Unrealized Losses	(1,716)	(1,837)
Total unrealized gains/(losses) on securities available for sale, Net Unrealized Gains	10,181	10,810
Income tax expense/(benefit), Gross Unrealized Gains	4,164	4,426
Income tax expense/(benefit), Gross Unrealized Losses	(601)	(643)
Income tax expense/(benefit), Net Unrealized Gains	3,563	3,783
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss)	7,733	8,221
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss)	(1,115)	(1,194)
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ 6,618	$ 7,027

Securities Available-for-Sale77

Securities Available-for-Sale - Amortized Cost and Fair Value of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 650,782	$ 629,463
Fair Value	660,963	640,273
Obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	46,329
Due after one year through five years, Amortized Cost	222,838
Due after five years through ten years, Amortized Cost	56,934
Due after ten years, Amortized Cost	79,762
Available-for-sale Securities, Debt Maturities, Amortized Cost	405,863
Due in one year or less, Fair Value	46,510
Due after one year through five years, Fair Value	224,334
Due after five years through ten years, Fair Value	58,793
Due after ten years, Fair Value	83,493
Fair Value, Debt securities	413,130
Collateralized mortgage obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	128,458	116,897
Fair Value	128,835	118,006
Residential mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	39,185	45,274
Fair Value	40,125	46,668
Commercial mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	69,697	39,834
Fair Value	69,204	39,673
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	643,203	621,884
Fair Value	651,294	631,214
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,579	7,579
Fair Value	$ 9,669	$ 9,059

Loans and Loans Held for Sale -

Loans and Loans Held for Sale - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)tdrloan	Dec. 31, 2014USD ($)loan	Mar. 04, 2015USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Deferred Income	$ 3,200,000	$ 2,100,000
Unamortized discount related to purchase accounting fair value adjustments	10,900,000	2,000,000
Loans	5,062,933,000	3,871,716,000
Loans held for sale	$ 35,321,000	$ 2,970,000
Percentage of commercial loans in total portfolio loans	76.00%	75.00%
Portfolio loans, net of unearned income	$ 3,836,877,000	$ 2,892,522,000
Maximum concentration of commercial real estate and commercial construction portfolio in loans	7.00%	9.00%
Number of loan modified | loan	39
Commitment to lend additional funds on TDRs	$ 0
Number of TDRs returned back to accruing status	8	9
Financial receivable trouble debt restructuring reclassified to accruing trouble debt restructuring status	$ 400,000	$ 1,900,000
Minimum period of loan payment defaults following restructure for TDRs to be in default	90 days
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 2,166,603,000	1,682,236,000
Portfolio loans, net of unearned income	$ 2,166,603,000	1,682,236,000
Number of loan modified | loan	8
Loans modified not considered to be troubled debt restructuring	$ 6,100,000
Commercial Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	413,444,000	216,148,000
Portfolio loans, net of unearned income	$ 413,444,000	216,148,000
Number of loan modified | loan	14
Loans modified not considered to be troubled debt restructuring	$ 8,500,000
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 639,372,000	489,586,000
Number of loan modified | loan	2
Loans modified not considered to be troubled debt restructuring	$ 100,000
Installment and Other Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	73,939,000	$ 65,567,000
Loans held for sale	23,300,000
CRE and Commercial Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio loans, net of unearned income	$ 2,600,000,000
Combined percentage of commercial real estate and commercial construction in total commercial loans	67.00%	66.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans	51.00%	49.00%
Out-of-state exposure of combined portfolio	5.80%	8.00%
Percentage of total loans out-of-state	3.00%	3.90%
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 1,256,830,000	$ 994,138,000
Portfolio loans, net of unearned income	$ 1,256,830,000	994,138,000
Number of loan modified | loan	11
Loans modified not considered to be troubled debt restructuring	$ 7,800,000
Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 470,845,000	418,563,000
Number of loan modified | loan	4
Loans modified not considered to be troubled debt restructuring	$ 400,000
Consumer Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,579,000	$ 2,508,000
Integrity Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	673,300,000
Loans	788,687,000		$ 788,700,000
Integrity Bancshares, Inc. | Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	293,200,000
Loans			331,600,000
Integrity Bancshares, Inc. | Commercial Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	69,200,000
Loans			92,400,000
Integrity Bancshares, Inc. | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	115,600,000
Loans			116,900,000
Integrity Bancshares, Inc. | Home Equity, Installment and Other Consumer Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans			27,500,000
Integrity Bancshares, Inc. | CRE and Commercial Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	424,000,000
Integrity Bancshares, Inc. | Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans			25,600,000
Integrity Bancshares, Inc. | Consumer Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans			1,900,000
Integrity Bancshares, Inc. | Consumer Borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans			36,100,000
Commercial and Industrial | Integrity Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 167,700,000
Loans			$ 184,200,000

Loans and Loans Held for Sale79

Loans and Loans Held for Sale - Composition of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Composition of the loans
Portfolio loans, net of unearned income	$ 3,836,877	$ 2,892,522
Consumer loans	1,190,735	976,224
Total Portfolio Loans	5,027,612	3,868,746
Loans held for sale	35,321	2,970
Total Loans	5,062,933	3,871,716
Commercial Real Estate
Composition of the loans
Portfolio loans, net of unearned income	2,166,603	1,682,236
Total Portfolio Loans	2,166,603	1,682,236
Total Loans	2,166,603	1,682,236
Commercial and Industrial
Composition of the loans
Portfolio loans, net of unearned income	1,256,830	994,138
Total Portfolio Loans	1,256,830	994,138
Total Loans	1,256,830	994,138
Commercial Construction
Composition of the loans
Portfolio loans, net of unearned income	413,444	216,148
Total Portfolio Loans	413,444	216,148
Total Loans	413,444	216,148
Residential Mortgage
Composition of the loans
Consumer loans	639,372	489,586
Total Loans	639,372	489,586
Home Equity
Composition of the loans
Consumer loans	470,845	418,563
Total Loans	470,845	418,563
Installment and Other Consumer
Composition of the loans
Consumer loans	73,939	65,567
Loans held for sale	23,300
Total Loans	73,939	65,567
Consumer Construction
Composition of the loans
Consumer loans	6,579	2,508
Total Loans	$ 6,579	$ 2,508

Loans and Loans Held for Sale80

Loans and Loans Held for Sale - Restructured Loans for Periods Presented (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Restructured loans	$ 6,338	$ 4,777
Performing TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans	23,955	36,983
Performing TDRs | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Restructured loans	6,822	16,939
Performing TDRs | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Restructured loans	6,321	8,074
Performing TDRs | Commercial Construction
Financing Receivable, Modifications [Line Items]
Restructured loans	5,013	5,736
Performing TDRs | Residential Mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans	2,590	2,839
Performing TDRs | Home Equity
Financing Receivable, Modifications [Line Items]
Restructured loans	3,184	3,342
Performing TDRs | Installment and Other Consumer
Financing Receivable, Modifications [Line Items]
Restructured loans	25	53
Nonperforming TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans	7,659	5,436
Nonperforming TDRs | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Restructured loans	3,548	2,180
Nonperforming TDRs | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Restructured loans	1,570	356
Nonperforming TDRs | Commercial Construction
Financing Receivable, Modifications [Line Items]
Restructured loans	1,265	1,869
Nonperforming TDRs | Residential Mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans	665	459
Nonperforming TDRs | Home Equity
Financing Receivable, Modifications [Line Items]
Restructured loans	523	562
Nonperforming TDRs | Installment and Other Consumer
Financing Receivable, Modifications [Line Items]
Restructured loans	88	10
Total TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans	31,614	42,419
Total TDRs | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Restructured loans	10,370	19,119
Total TDRs | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Restructured loans	7,891	8,430
Total TDRs | Commercial Construction
Financing Receivable, Modifications [Line Items]
Restructured loans	6,278	7,605
Total TDRs | Residential Mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans	3,255	3,298
Total TDRs | Home Equity
Financing Receivable, Modifications [Line Items]
Restructured loans	3,707	3,904
Total TDRs | Installment and Other Consumer
Financing Receivable, Modifications [Line Items]
Restructured loans	$ 113	$ 63

Loans and Loans Held for Sale81

Loans and Loans Held for Sale - Restructured Loans for Periods Stated (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)loan	Dec. 31, 2014USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	60	44
Pre-Modification Outstanding Recorded Investment	$ 8,290	$ 4,949
Post-Modification Outstanding Recorded Investment	6,338	4,777
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (1,952)	$ (172)
Principal Deferral
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	8	6
Pre-Modification Outstanding Recorded Investment	$ 3,512	$ 2,372
Post-Modification Outstanding Recorded Investment	2,204	2,321
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (1,308)	$ (51)
Interest Rate Reduction and Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	4	2
Pre-Modification Outstanding Recorded Investment	$ 410	$ 96
Post-Modification Outstanding Recorded Investment	406	95
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (4)	$ (1)
Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	17	7
Pre-Modification Outstanding Recorded Investment	$ 3,312	$ 1,368
Post-Modification Outstanding Recorded Investment	2,922	1,322
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (390)	$ (46)
Chapter 7 Bankruptcy
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	31	29
Pre-Modification Outstanding Recorded Investment	$ 1,056	$ 1,113
Post-Modification Outstanding Recorded Investment	806	1,039
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (250)	$ (74)
Commercial Real Estate | Principal Deferral
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2	4
Pre-Modification Outstanding Recorded Investment	$ 2,851	$ 1,991
Post-Modification Outstanding Recorded Investment	1,841	1,965
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (1,010)	$ (26)
Commercial Real Estate | Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3
Pre-Modification Outstanding Recorded Investment	$ 438
Post-Modification Outstanding Recorded Investment	427
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (11)
Commercial and Industrial | Principal Deferral
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	6	2
Pre-Modification Outstanding Recorded Investment	$ 661	$ 381
Post-Modification Outstanding Recorded Investment	363	356
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (298)	$ (25)
Commercial and Industrial | Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2
Pre-Modification Outstanding Recorded Investment	$ 824
Post-Modification Outstanding Recorded Investment	728
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (96)
Commercial Construction | Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	1
Pre-Modification Outstanding Recorded Investment	$ 1,434	$ 1,019
Post-Modification Outstanding Recorded Investment	1,432	974
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (2)	$ (45)
Residential Mortgage | Interest Rate Reduction and Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1
Pre-Modification Outstanding Recorded Investment	$ 207
Post-Modification Outstanding Recorded Investment	205
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (2)
Residential Mortgage | Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	8
Pre-Modification Outstanding Recorded Investment	$ 545
Post-Modification Outstanding Recorded Investment	265
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (280)
Residential Mortgage | Chapter 7 Bankruptcy
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	7	9
Pre-Modification Outstanding Recorded Investment	$ 428	$ 651
Post-Modification Outstanding Recorded Investment	226	634
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (202)	$ (17)
Home Equity | Interest Rate Reduction and Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	2
Pre-Modification Outstanding Recorded Investment	$ 203	$ 96
Post-Modification Outstanding Recorded Investment	201	95
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (2)	$ (1)
Home Equity | Maturity Date Extension
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1	6
Pre-Modification Outstanding Recorded Investment	$ 71	$ 349
Post-Modification Outstanding Recorded Investment	70	348
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (1)	$ (1)
Home Equity | Chapter 7 Bankruptcy
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	23	15
Pre-Modification Outstanding Recorded Investment	$ 619	$ 432
Post-Modification Outstanding Recorded Investment	576	382
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (43)	$ (50)
Installment and Other Consumer | Chapter 7 Bankruptcy
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1	5
Pre-Modification Outstanding Recorded Investment	$ 9	$ 30
Post-Modification Outstanding Recorded Investment	4	23
Increase (Decrease) Financing Receivable Modifications Difference In Recorded Investments	$ (5)	$ (7)

Loans and Loans Held for Sale82

Loans and Loans Held for Sale - Summary of Nonperforming Assets of Defaulted TDRs (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)contractloan	Dec. 31, 2014USD ($)contract
Financing Receivable, Modifications [Line Items]
Number of loan modified | loan	39
Number of Defaults | contract	0	3
Recorded Investment	$ 0	$ 64
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Number of loan modified | loan	8
Loans modified not considered to be troubled debt restructuring	$ 6,100
Number of Defaults | contract	0	0
Recorded Investment	$ 0	$ 0
Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Number of loan modified | loan	11
Loans modified not considered to be troubled debt restructuring	$ 7,800
Number of Defaults | contract	0	0
Recorded Investment	$ 0	$ 0
Commercial Construction
Financing Receivable, Modifications [Line Items]
Number of loan modified | loan	14
Loans modified not considered to be troubled debt restructuring	$ 8,500
Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of Defaults | contract	0	1
Recorded Investment	$ 0	$ 20
Home Equity
Financing Receivable, Modifications [Line Items]
Number of loan modified | loan	4
Loans modified not considered to be troubled debt restructuring	$ 400
Number of Defaults | contract	0	2
Recorded Investment	$ 0	$ 44
Residential Mortgage
Financing Receivable, Modifications [Line Items]
Number of loan modified | loan	2
Loans modified not considered to be troubled debt restructuring	$ 100

Loans and Loans Held for Sale83

Loans and Loans Held for Sale - Summary of Nonperforming Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Net Nonperforming Assets, Assumed in Business Acquisitions	$ 16,300
Nonperforming Assets
Nonaccrual loans	27,723	$ 7,021
Nonaccrual TDRs	7,659	5,436
Total nonaccrual loans	35,382	12,457
OREO	354	166
Total Nonperforming Assets	35,736	12,623
Commercial and Industrial
Nonperforming Assets
Total nonaccrual loans	9,279	$ 1,622
Total Nonperforming Assets	$ 4,700

Loans and Loans Held for Sale84

Loans and Loans Held for Sale - Summary of Aggregate Amount of Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Loans Receivable from Officers and Directors [Roll Forward]
Balance at beginning of year	$ 27,368	$ 23,848
New loans	24,743	27,799
Repayments	(27,594)	(24,279)
Balance at End of Year	$ 24,517	$ 27,368

Allowance for Loan Losses - Age

Allowance for Loan Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	$ 5,002,925	$ 3,850,597
Loans, Past Due	60,008	21,119
Loans, Non-performing	35,382	12,457
Total Loans	5,062,933	3,871,716
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	2,145,655	1,674,930
Loans, Past Due	20,948	7,306
Loans, Non-performing	8,719	4,435
Total Loans	2,166,603	1,682,236
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	1,244,802	991,136
Loans, Past Due	12,028	3,002
Loans, Non-performing	9,279	1,622
Total Loans	1,256,830	994,138
Commercial Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	401,084	214,174
Loans, Past Due	12,360	1,974
Loans, Non-performing	8,753	1,974
Total Loans	413,444	216,148
Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	631,085	485,465
Loans, Past Due	8,287	4,121
Loans, Non-performing	5,629	2,336
Total Loans	639,372	489,586
Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	465,055	414,303
Loans, Past Due	5,790	4,260
Loans, Non-performing	2,902	2,059
Total Loans	470,845	418,563
Installment and Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	73,486	65,111
Loans, Past Due	453	456
Loans, Non-performing	100	31
Total Loans	73,939	65,567
Consumer Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	6,579	2,508
Loans, Past Due	0	0
Loans, Non-performing	0	0
Total Loans	6,579	2,508
Loans Held for Sale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Current	35,179	2,970
Loans, Past Due	142	0
Loans, Non-performing	0	0
Total Loans	35,321	2,970
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	22,001	6,448
30-59 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	11,602	2,548
30-59 Days Past Due | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	2,453	1,227
30-59 Days Past Due | Commercial Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	3,517	0
30-59 Days Past Due | Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	1,728	565
30-59 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	2,365	1,756
30-59 Days Past Due | Installment and Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	242	352
30-59 Days Past Due | Consumer Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	0	0
30-59 Days Past Due | Loans Held for Sale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	94	0
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	2,625	2,214
60-89 Days Past Due | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	627	323
60-89 Days Past Due | Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	296	153
60-89 Days Past Due | Commercial Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	90	0
60-89 Days Past Due | Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	930	1,220
60-89 Days Past Due | Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	523	445
60-89 Days Past Due | Installment and Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	111	73
60-89 Days Past Due | Consumer Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	0	0
60-89 Days Past Due | Loans Held for Sale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Past Due	$ 48	$ 0

Allowance for Loan Losses - Rec

Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 3,836,877	$ 2,892,522
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 3,653,344	$ 2,780,315
Total percentage of recorded investment in commercial loan	95.20%	96.10%
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 83,680	$ 65,968
Total percentage of recorded investment in commercial loan	2.20%	2.30%
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 99,853	$ 46,239
Total percentage of recorded investment in commercial loan	2.60%	1.60%
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 2,166,603	$ 1,682,236
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 2,094,851	$ 1,635,132
Total percentage of recorded investment in commercial loan	96.70%	97.20%
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 19,938	$ 23,597
Total percentage of recorded investment in commercial loan	0.90%	1.40%
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 51,814	$ 23,507
Total percentage of recorded investment in commercial loan	2.40%	1.40%
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 1,256,830	$ 994,138
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 1,182,685	$ 948,663
Total percentage of recorded investment in commercial loan	94.10%	95.40%
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 43,896	$ 30,357
Total percentage of recorded investment in commercial loan	3.50%	3.10%
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 30,249	$ 15,118
Total percentage of recorded investment in commercial loan	2.40%	1.50%
Commercial Construction
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 413,444	$ 216,148
Total percentage of recorded investment in commercial loan	100.00%	100.00%
Commercial Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 375,808	$ 196,520
Total percentage of recorded investment in commercial loan	90.90%	90.90%
Commercial Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 19,846	$ 12,014
Total percentage of recorded investment in commercial loan	4.80%	5.60%
Commercial Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment in commercial loan	$ 17,790	$ 7,614
Total percentage of recorded investment in commercial loan	4.30%	3.50%

Allowance for Loan Losses - R87

Allowance for Loan Losses - Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 1,190,735	$ 976,224
% of Total	100.00%	100.00%
Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 1,182,104	$ 971,798
% of Total	99.30%	99.50%
Non Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 8,631	$ 4,426
% of Total	0.70%	0.50%
Residential Mortgage
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 639,372	$ 489,586
% of Total	100.00%	100.00%
Residential Mortgage | Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 633,743	$ 487,250
% of Total	99.10%	99.50%
Residential Mortgage | Non Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 5,629	$ 2,336
% of Total	0.90%	0.50%
Home Equity
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 470,845	$ 418,563
% of Total	100.00%	100.00%
Home Equity | Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 467,943	$ 416,504
% of Total	99.40%	99.50%
Home Equity | Non Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 2,902	$ 2,059
% of Total	0.60%	0.50%
Installment and Other Consumer
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 73,939	$ 65,567
% of Total	100.00%	100.00%
Installment and Other Consumer | Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 73,839	$ 65,536
% of Total	99.80%	99.90%
Installment and Other Consumer | Non Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 100	$ 31
% of Total	0.20%	0.10%
Consumer Construction
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 6,579	$ 2,508
% of Total	100.00%	100.00%
Consumer Construction | Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 6,579	$ 2,508
% of Total	100.00%	100.00%
Consumer Construction | Non Performing Consumer Loan
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in consumer loan	$ 0	$ 0
% of Total	0.00%	0.00%

Allowance for Loan Losses - Add

Allowance for Loan Losses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Impaired financing receivables	$ 45,650	$ 43,977
Acquired loans that experienced credit deterioration since acquisition	$ 9,900
Minimum period interest and principal of loans past due considered nonperforming (in days)	90 days
Evaluation for impairment of substandard and nonaccrual commercial loans	$ 500

Allowance for Loan Losses - Inv

Allowance for Loan Losses - Investments in Loans Considered to be Impaired and Related Information on Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment	$ 618	$ 63
With a related allowance recorded, Unpaid Principal Balance	1,468	63
With a related allowance recorded, Related Allowance	37	54
Without a related allowance recorded, Recorded Investment	45,032	43,914
Without a related allowance, Unpaid Principal Balance	50,286	53,785
Without a related allowance recorded, Related Allowance	0	0
Impaired financing receivables	45,650	43,977
Impaired Financing Receivable, Unpaid Principal Balance, Total	51,754	53,848
Impaired Financing Receivable, Related Allowance, Total	37	54
With a related allowance recorded, Average Recorded Investment	956	72
With a related allowance recorded, Interest Income Recognized	7	6
Without a related allowance recorded, Average Recorded Investment	46,638	44,978
Without a related allowance recorded, Interest Income Recognized	1,741	1,550
Impaired Financing Receivable, Average Recorded Investment, Total	47,594	45,050
Impaired Financing Receivable, Interest Income Recognized, Total	1,748	1,556
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment	0	0
With a related allowance recorded, Unpaid Principal Balance	0	0
With a related allowance recorded, Related Allowance	0	0
Without a related allowance recorded, Recorded Investment	12,661	19,890
Without a related allowance, Unpaid Principal Balance	13,157	25,262
Without a related allowance recorded, Related Allowance	0	0
Impaired financing receivables	12,661	19,890
Impaired Financing Receivable, Unpaid Principal Balance, Total	13,157	25,262
Impaired Financing Receivable, Related Allowance, Total	0	0
With a related allowance recorded, Average Recorded Investment	0	0
With a related allowance recorded, Interest Income Recognized	0	0
Without a related allowance recorded, Average Recorded Investment	14,622	20,504
Without a related allowance recorded, Interest Income Recognized	597	684
Impaired Financing Receivable, Average Recorded Investment, Total	14,622	20,504
Impaired Financing Receivable, Interest Income Recognized, Total	597	684
Commercial and Industrial
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment	0	0
With a related allowance recorded, Unpaid Principal Balance	0	0
With a related allowance recorded, Related Allowance	0	0
Without a related allowance recorded, Recorded Investment	14,417	9,218
Without a related allowance, Unpaid Principal Balance	15,220	9,449
Without a related allowance recorded, Related Allowance	0	0
Impaired financing receivables	14,417	9,218
Impaired Financing Receivable, Unpaid Principal Balance, Total	15,220	9,449
Impaired Financing Receivable, Related Allowance, Total	0	0
With a related allowance recorded, Average Recorded Investment	0	0
With a related allowance recorded, Interest Income Recognized	0	0
Without a related allowance recorded, Average Recorded Investment	14,416	9,246
Without a related allowance recorded, Interest Income Recognized	450	241
Impaired Financing Receivable, Average Recorded Investment, Total	14,416	9,246
Impaired Financing Receivable, Interest Income Recognized, Total	450	241
Commercial Construction
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment	500	0
With a related allowance recorded, Unpaid Principal Balance	1,350	0
With a related allowance recorded, Related Allowance	3	0
Without a related allowance recorded, Recorded Investment	10,998	7,605
Without a related allowance, Unpaid Principal Balance	14,200	11,293
Without a related allowance recorded, Related Allowance	0	0
Impaired financing receivables	11,498	7,605
Impaired Financing Receivable, Unpaid Principal Balance, Total	15,550	11,293
Impaired Financing Receivable, Related Allowance, Total	3	0
With a related allowance recorded, Average Recorded Investment	834	0
With a related allowance recorded, Interest Income Recognized	0	0
Without a related allowance recorded, Average Recorded Investment	10,581	8,145
Without a related allowance recorded, Interest Income Recognized	329	227
Impaired Financing Receivable, Average Recorded Investment, Total	11,415	8,145
Impaired Financing Receivable, Interest Income Recognized, Total	329	227
Consumer Real Estate
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment	116	43
With a related allowance recorded, Unpaid Principal Balance	116	43
With a related allowance recorded, Related Allowance	32	43
Without a related allowance recorded, Recorded Investment	6,845	7,159
Without a related allowance, Unpaid Principal Balance	7,521	7,733
Without a related allowance recorded, Related Allowance	0	0
Impaired financing receivables	6,961	7,202
Impaired Financing Receivable, Unpaid Principal Balance, Total	7,637	7,776
Impaired Financing Receivable, Related Allowance, Total	32	43
With a related allowance recorded, Average Recorded Investment	120	48
With a related allowance recorded, Interest Income Recognized	7	4
Without a related allowance recorded, Average Recorded Investment	6,902	7,027
Without a related allowance recorded, Interest Income Recognized	364	396
Impaired Financing Receivable, Average Recorded Investment, Total	7,022	7,075
Impaired Financing Receivable, Interest Income Recognized, Total	371	400
Other Consumer
Financing Receivable, Impaired [Line Items]
With a related allowance recorded, Recorded Investment	2	20
With a related allowance recorded, Unpaid Principal Balance	2	20
With a related allowance recorded, Related Allowance	2	11
Without a related allowance recorded, Recorded Investment	111	42
Without a related allowance, Unpaid Principal Balance	188	48
Without a related allowance recorded, Related Allowance	0	0
Impaired financing receivables	113	62
Impaired Financing Receivable, Unpaid Principal Balance, Total	190	68
Impaired Financing Receivable, Related Allowance, Total	2	11
With a related allowance recorded, Average Recorded Investment	2	24
With a related allowance recorded, Interest Income Recognized	0	2
Without a related allowance recorded, Average Recorded Investment	117	56
Without a related allowance recorded, Interest Income Recognized	1	2
Impaired Financing Receivable, Average Recorded Investment, Total	119	80
Impaired Financing Receivable, Interest Income Recognized, Total	$ 1	$ 4

Allowance for Loan Losses - Sum

Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 04, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				$ 47,911,000				$ 46,255,000	$ 47,911,000	$ 46,255,000
Charge-offs									(15,266,000)	(6,353,000)
Recoveries									5,114,000	6,294,000
Net (Charge-offs)/ Recoveries									(10,152,000)	(59,000)
Provision for loan losses	$ 3,915,000	$ 3,206,000	$ 2,059,000	1,207,000	$ 1,106,000	$ 1,454,000	$ (1,134,000)	289,000	10,388,000	1,715,000	$ 8,311,000
Balance at End of Year	48,147,000				47,911,000				48,147,000	47,911,000	46,255,000
Total Loans	5,062,933,000				3,871,716,000				5,062,933,000	3,871,716,000
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				20,164,000				18,921,000	20,164,000	18,921,000
Charge-offs									(2,787,000)	(2,041,000)
Recoveries									3,545,000	1,798,000
Net (Charge-offs)/ Recoveries									758,000	(243,000)
Provision for loan losses									(5,879,000)	1,486,000
Balance at End of Year	15,043,000				20,164,000				15,043,000	20,164,000	18,921,000
Total Loans	2,166,603,000				1,682,236,000				2,166,603,000	1,682,236,000
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				13,668,000				14,433,000	13,668,000	14,433,000
Charge-offs									(5,463,000)	(1,267,000)
Recoveries									605,000	3,647,000
Net (Charge-offs)/ Recoveries									(4,858,000)	2,380,000
Provision for loan losses									2,043,000	(3,145,000)
Balance at End of Year	10,853,000				13,668,000				10,853,000	13,668,000	14,433,000
Total Loans	1,256,830,000				994,138,000				1,256,830,000	994,138,000
Commercial Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				6,093,000				5,374,000	6,093,000	5,374,000
Charge-offs									(3,321,000)	(712,000)
Recoveries									143,000	146,000
Net (Charge-offs)/ Recoveries									(3,178,000)	(566,000)
Provision for loan losses									9,710,000	1,285,000
Balance at End of Year	12,625,000				6,093,000				12,625,000	6,093,000	5,374,000
Total Loans	413,444,000				216,148,000				413,444,000	216,148,000
Consumer Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				6,333,000				6,362,000	6,333,000	6,362,000
Charge-offs									(2,167,000)	(1,200,000)
Recoveries									495,000	350,000
Net (Charge-offs)/ Recoveries									(1,672,000)	(850,000)
Provision for loan losses									3,739,000	821,000
Balance at End of Year	8,400,000				6,333,000				8,400,000	6,333,000	6,362,000
Other Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year				$ 1,653,000				$ 1,165,000	1,653,000	1,165,000
Charge-offs									(1,528,000)	(1,133,000)
Recoveries									326,000	353,000
Net (Charge-offs)/ Recoveries									(1,202,000)	(780,000)
Provision for loan losses									775,000	1,268,000
Balance at End of Year	1,226,000				$ 1,653,000				1,226,000	$ 1,653,000	$ 1,165,000
Integrity Bancshares, Inc.
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Allowance for Loan Losses	0								0			$ 0
Total Loans	673,300,000								673,300,000
Loans	788,687,000								788,687,000			788,700,000
Integrity Bancshares, Inc. | Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Total Loans	293,200,000								293,200,000
Loans												331,600,000
Integrity Bancshares, Inc. | Commercial Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Total Loans	$ 69,200,000								$ 69,200,000
Loans												$ 92,400,000

Allowance for Loan Losses - S91

Allowance for Loan Losses - Summary of Allowance for Loan Losses and Recorded Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 37	$ 54
Allowance for Loan Losses, Collectively Evaluated for Impairment	48,110	47,857
Total Allowance for Loan Losses	48,147	47,911	$ 46,255
Portfolio Loans, Individually Evaluated for Impairment	45,650	43,977
Portfolio Loans, Collectively Evaluated for Impairment	4,981,962	3,824,769
Total Portfolio Loans	5,027,612	3,868,746
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	15,043	20,164
Total Allowance for Loan Losses	15,043	20,164	18,921
Portfolio Loans, Individually Evaluated for Impairment	12,661	19,890
Portfolio Loans, Collectively Evaluated for Impairment	2,153,942	1,662,346
Total Portfolio Loans	2,166,603	1,682,236
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	10,853	13,668
Total Allowance for Loan Losses	10,853	13,668	14,433
Portfolio Loans, Individually Evaluated for Impairment	14,417	9,218
Portfolio Loans, Collectively Evaluated for Impairment	1,242,413	984,920
Total Portfolio Loans	1,256,830	994,138
Commercial Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	3	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	12,622	6,093
Total Allowance for Loan Losses	12,625	6,093	5,374
Portfolio Loans, Individually Evaluated for Impairment	11,498	7,605
Portfolio Loans, Collectively Evaluated for Impairment	401,946	208,543
Total Portfolio Loans	413,444	216,148
Consumer Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	32	43
Allowance for Loan Losses, Collectively Evaluated for Impairment	8,368	6,290
Total Allowance for Loan Losses	8,400	6,333	6,362
Portfolio Loans, Individually Evaluated for Impairment	6,961	7,202
Portfolio Loans, Collectively Evaluated for Impairment	1,109,835	903,455
Total Portfolio Loans	1,116,796	910,657
Other Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	2	11
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,224	1,642
Total Allowance for Loan Losses	1,226	1,653	$ 1,165
Portfolio Loans, Individually Evaluated for Impairment	113	62
Portfolio Loans, Collectively Evaluated for Impairment	73,826	65,505
Total Portfolio Loans	$ 73,939	$ 65,567

Premises and Equipment - Summar

Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 98,396	$ 84,089
Accumulated depreciation	(49,269)	(45,923)
Premises and equipment, net	49,127	38,166
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	8,699	6,193
Premises
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	52,968	44,690
Furniture and Equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	29,543	26,661
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 7,186	$ 6,545

Premises and Equipment - Additi

Premises and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 4,739	$ 3,465	$ 3,507
Lease expiration year	Jan. 1, 2054
Rental expense	$ 3,900	2,700	2,500
Two Directors
Property, Plant and Equipment [Line Items]
Rental expense for premises leases with two directors	$ 200	$ 200	$ 200

Premises and Equipment - Minimu

Premises and Equipment - Minimum Annual Rental and Renewal Option Payments (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Property, Plant and Equipment [Abstract]
Operating, 2016	$ 2,860
Operating, 2017	2,895
Operating, 2018	2,899
Operating, 2019	2,913
Operating, 2020	2,857
Operating, Thereafter	53,107
Operating, Total	67,531
Capital, 2016	76
Capital, 2017	76
Capital, 2018	76
Capital, 2019	77
Capital, 2020	77
Capital, Thereafter	610
Capital, Total	992
2,016	2,936
2,017	2,971
2,018	2,975
2,019	2,990
2,020	2,934
Thereafter	53,717
Total	$ 68,523

Goodwill and Other Intangible95

Goodwill and Other Intangible Assets - Roll Forward of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Roll Forward]
Balance at beginning of year	$ 175,820	$ 175,820
Additions	115,944	0
Balance at End of Year	$ 291,764	$ 175,820

Goodwill and Other Intangible96

Goodwill and Other Intangible Assets - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)event	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill acquired	$ 115,944	$ 0
Acquisition of core deposits	6,100
Acquisition of wealth management relationships	100
Acquisition of insurance contract relationships	400
Finite-lived Intangible Assets Acquired	$ 5,713	0
Number of triggering events | event	0
Amortization expense on finite-lived intangible assets	$ 1,818	$ 1,129	$ 1,591

Goodwill and Other Intangible97

Goodwill and Other Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Gross carrying amount at beginning of year	$ 16,401	$ 16,401
Additions	5,713	0
Accumulated amortization	(15,589)	(13,770)
Gross carrying amount at end of year	$ 6,525	$ 2,631

Goodwill and Other Intangible98

Goodwill and Other Intangible Assets - Summary of Expected Amortization Expense for Finite-Lived Intangibles Assets (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,016	$ 1,433
2,017	1,149
2,018	668
2,019	561
2,020	475
Total	$ 4,286

Derivative Instruments and He99

Derivative Instruments and Hedging Activities - Value of Derivative Assets and Derivative Liabilities (Detail) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	$ 11,295	$ 12,981
Fair value, Derivatives (included in Other Liabilities)	11,276	12,953
Collateral posted, Derivatives (included in Other Liabilities)	12,573	12,059
Other Assets | Interest Rate Swap Contracts-Commercial Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	11,295	12,981
Notional amount, Derivatives (included in Other Assets)	245,595	245,152
Other Assets | Interest Rate Lock Commitments-Mortgage Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	261	235
Notional amount, Derivatives (included in Other Assets)	9,894	8,822
Other Assets | Forward Sale Contracts-Mortgage Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	0	0
Notional amount, Derivatives (included in Other Assets)	0	0
Other Liabilities | Interest Rate Swap Contracts-Commercial Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	11,276	12,953
Notional amount, Derivatives (included in Other Liabilities)	245,595	245,152
Collateral posted, Derivatives (included in Other Liabilities)	12,753	12,059
Other Liabilities | Forward Sale Contracts-Mortgage Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	5	57
Notional amount, Derivatives (included in Other Liabilities)	$ 9,800	$ 7,789

Derivative Instruments and H100

Derivative Instruments and Hedging Activities - Schedule of Gross Amounts of Derivative Assets and Derivative Liabilities (Detail) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivatives not Designated as Hedging Instruments
Gross amounts recognized	$ 11,295	$ 13,203
Gross amounts offset	0	(222)
Net amounts presented in the Consolidated Balance Sheets	11,295	12,981
Net Amount	11,295	12,981
Gross amounts recognized	11,276	13,175
Gross amounts offset	0	(222)
Net amounts presented in the Consolidated Balance Sheets	11,276	12,953
Collateral Already Posted, Aggregate Fair Value	(12,573)	(12,059)
Net Amount	$ (1,297)	$ 894

Derivative Instruments and H101

Derivative Instruments and Hedging Activities - Amount of Gain or Loss Recognized in Income on Derivatives (Detail) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivative Gain (Loss)	$ 70	$ 36	$ (474)
Interest Rate Swap Contracts-Commercial Loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivative Gain (Loss)	(8)	(24)	(174)
Interest Rate Lock Commitments-Mortgage Loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivative Gain (Loss)	26	150	(382)
Forward Sale Contracts-Mortgage Loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivative Gain (Loss)	$ 52	$ (90)	$ 82

Mortgage Servicing Rights - Add

Mortgage Servicing Rights - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Mortgage Loan Activity [Line Items]
Sale of 1-4 family mortgage loans to Federal National Mortgage Association (FNMA)	$ 99,458	$ 42,361	$ 87,932
Total servicing portfolio	361,200	325,800	327,400
Federal National Mortgage Association or (FNMA)
Mortgage Loan Activity [Line Items]
Sale of 1-4 family mortgage loans to Federal National Mortgage Association (FNMA)	$ 76,800	$ 40,100	$ 62,900

Mortgage Servicing Rights - Sch

Mortgage Servicing Rights - Schedule of Mortgage Servicing Rights and Net Carrying Values (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Servicing Rights
Mortgage Loan on Real Estate, Write-down or Reserve [Roll Forward]
Beginning balance	$ 3,108	$ 3,208
Additions	856	431
Amortization	(538)	(531)
Ending balance	3,426	3,108
Valuation Allowances and Reserves [Domain]
Mortgage Loan on Real Estate, Write-down or Reserve [Roll Forward]
Beginning balance	(291)	(289)
Temporary impairment recapture	102	(2)
Ending balance	(189)	(291)
Net Carrying Value
Mortgage Loan on Real Estate, Write-down or Reserve [Roll Forward]
Beginning balance	2,817	2,919
Additions	856	431
Amortization	(538)	(531)
Temporary impairment recapture	102	(2)
Ending balance	$ 3,237	$ 2,817

Qualified Affordable Housing (D

Qualified Affordable Housing (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments in Affordable Housing Projects [Abstract]
Amortization Method Qualified Affordable Housing Project Investments	$ 15,000,000	$ 18,600,000
Qualified Affordable Housing Project Investments, Commitment	0	0
Amortization Method Qualified Affordable Housing Project Investments, Amortization	3,600,000	4,100,000	$ 4,100,000
Affordable Housing Tax Credits and Other Tax Benefits, Amount	$ 4,000,000	$ 4,300,000	$ 4,300,000

Deposits - Composition of Depos

Deposits - Composition of Deposits and Interest Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	$ 4,876,611	$ 3,908,842	$ 3,672,308
Interest Expense	12,944	10,128	11,406
Noninterest-bearing Demand
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,227,766	1,083,919	992,779
Interest-bearing Demand
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	616,188	335,099	312,790
Interest Expense	818	19	75
Money Market
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	605,184	376,612	281,403
Interest Expense	1,299	572	446
Savings
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,061,265	1,027,095	994,805
Interest Expense	1,712	1,607	1,735
Certificates of Deposit
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,366,208	1,086,117	1,090,531
Interest Expense	$ 9,115	$ 7,930	$ 9,150

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Banking and Thrift [Abstract]
Aggregate value of certificate of deposit over $100,000	$ 521.6	$ 382.2

Deposits - Scheduled Maturities

Deposits - Scheduled Maturities of Certificates of Deposit (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Banking and Thrift [Abstract]
2,016	$ 870,679
2,017	304,820
2,018	102,886
2,019	37,742
2,020	41,808
Thereafter	8,273
Total	$ 1,366,208	$ 1,086,117

Short-Term Borrowings - Composi

Short-Term Borrowings - Composition of Short-Term Borrowings, Interest Expense and Weighted Average Interest Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-term Debt [Line Items]
Balance	$ 418,086	$ 320,605	$ 173,847
Weighted Average Interest Rate	0.44%	0.27%	0.24%
Interest Expense	$ 936	$ 514	$ 341
REPOs
Short-term Debt [Line Items]
Balance	$ 62,086	$ 30,605	$ 33,847
Weighted Average Interest Rate	0.01%	0.01%	0.01%
Interest Expense	$ 4	$ 3	$ 62
FHLB Advances
Short-term Debt [Line Items]
Balance	$ 356,000	$ 290,000	$ 140,000
Weighted Average Interest Rate	0.52%	0.31%	0.30%
Interest Expense	$ 932	$ 511	$ 279
Collateralized Mortgage Backed Securities
Short-term Debt [Line Items]
Carrying amount of mortgage back securities pledged as collateral	$ 67,000	$ 35,600

Long-Term Borrowings and Sub109

Long-Term Borrowings and Subordinated Debt - Additional Information (Detail) - USD ($)	Jun. 18, 2015	Mar. 05, 2015	Jun. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 04, 2015
Debt Instrument [Line Items]
Early repayment of junior subordinated debt			$ 45,000,000	$ 13,500,000	$ 0	$ 45,000,000
Long-term borrowings				117,000,000	$ 19,300,000
Total loans pledged as collateral				2,800,000,000
Maximum eligible borrowing based on qualifying collateral				1,400,000,000
Maximum borrowing capacity				1,900,000,000
Capital lease				$ 200,000
Percentage of equity owned				100.00%
2006 Junior Subordinated Debt | Integrity Bancshares, Inc.
Debt Instrument [Line Items]
Junior Subordinated Debt Assumed on Acquisition							$ 13,500,000
Junior Subordinated Debt Paid Off	$ 5,000,000	$ 8,500,000

Long-Term Borrowings and Sub110

Long-Term Borrowings and Subordinated Debt - Schedule of Long-Term Borrowings, Interest Expense and Weighted Average Interest Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
Long-term borrowings	$ 117,043	$ 19,442	$ 21,810
Weighted average interest rate	0.81%	3.00%	3.01%
Interest expense	$ 790	$ 617	$ 746

Long-Term Borrowings and Sub111

Long-Term Borrowings and Subordinated Debt - Schedule of Annual Maturities and Average Interest Rate of Long-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
2016 Balance	$ 102,330
2017 Balance	2,412
2018 Balance	2,496
2019 Balance	2,514
2020 Balance	2,004
Thereafter Balance	5,287
Total Long-term Balance	$ 117,043	$ 19,442	$ 21,810
2016 Average Rate	0.52%
2017 Average Rate	3.52%
2018 Average Rate	3.60%
2019 Average Rate	3.13%
2020 Average Rate	3.22%
Thereafter Average Rate	1.85%
Total Average Rate	0.81%

Long-Term Borrowings and Sub112

Long-Term Borrowings and Subordinated Debt - Schedule of Junior Subordinated Debt Securities and Interest Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Junior Subordinated Debentures [Line Items]
Balance	$ 45,619	$ 45,619	$ 45,619
Interest Expense	1,327	1,222	2,070
2006 Junior Subordinated Debt
Junior Subordinated Debentures [Line Items]
Balance	25,000	25,000	25,000
Interest Expense	554	463	475
2008 Junior Subordinated Debt-Trust Preferred Securities
Junior Subordinated Debentures [Line Items]
Balance	20,619	20,619	20,619
Interest Expense	773	759	770
2008 Junior Subordinated Debt
Junior Subordinated Debentures [Line Items]
Balance	0	0	0
Interest Expense	0	0	422
2008 Junior Subordinated Debt
Junior Subordinated Debentures [Line Items]
Balance	0	0	0
Interest Expense	$ 0	$ 0	$ 403

Long-Term Borrowings and Sub113

Long-Term Borrowings and Subordinated Debt - Schedule of Junior Subordinated Debt Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Junior Subordinated Debentures [Line Items]
Junior subordinated debt securities	$ 45,619	$ 45,619	$ 45,619
Interest Rate at December 31, 2015	0.81%	3.00%	3.01%
2006 Junior Subordinated Debt
Junior Subordinated Debentures [Line Items]
Junior subordinated debt securities	$ 25,000	$ 25,000	$ 25,000
Stated Maturity Date	Dec. 15, 2036
Optional redemption date at par	Any time after 9/15/2011
Regulatory Capital	Tier 2
Interest Rate at December 31, 2015	2.11%
2006 Junior Subordinated Debt | 3-Month LIBOR
Junior Subordinated Debentures [Line Items]
Basis spread on base interest rate	1.60%
2008 Junior Subordinated Debt-Trust Preferred Securities
Junior Subordinated Debentures [Line Items]
Junior subordinated debt securities	$ 20,619	$ 20,619	$ 20,619
Trust Preferred Securities	$ 20,619
Stated Maturity Date	Mar. 15, 2038
Optional redemption date at par	Any time after 3/15/2013
Regulatory Capital	Tier 1
Interest Rate at December 31, 2015	4.01%
2008 Junior Subordinated Debt-Trust Preferred Securities | 3-Month LIBOR
Junior Subordinated Debentures [Line Items]
Basis spread on base interest rate	3.50%
2008 Junior Subordinated Debt
Junior Subordinated Debentures [Line Items]
Junior subordinated debt securities	$ 20,000
Stated Maturity Date	Jun. 15, 2018
Optional redemption date at par	Any time after 6/15/2013
Regulatory Capital	Tier 2
Interest Rate at December 31, 2015	0.00%
2008 Junior Subordinated Debt | 3-Month LIBOR
Junior Subordinated Debentures [Line Items]
Basis spread on base interest rate	3.50%
2008 Junior Subordinated Debt
Junior Subordinated Debentures [Line Items]
Junior subordinated debt securities	$ 25,000
Stated Maturity Date	May 30, 2018
Optional redemption date at par	Any time after 5/30/2013
Regulatory Capital	Tier 2
Interest Rate at December 31, 2015	0.00%
2008 Junior Subordinated Debt | 3-Month LIBOR
Junior Subordinated Debentures [Line Items]
Basis spread on base interest rate	2.50%

Commitments and Contingencies -

Commitments and Contingencies - Commitments and Letters of Credit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Commitment And Contingencies [Line Items]
Commitments and letters of credit	$ 1,717,530	$ 1,232,212
Standby Letters of Credit
Commitment And Contingencies [Line Items]
Commitments and letters of credit	97,676	73,584
Commitments to Extend Credit
Commitment And Contingencies [Line Items]
Commitments and letters of credit	$ 1,619,854	$ 1,158,628

Commitments and Contingencie115

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]
Allowance for unfunded commitments	$ 2,500,000	$ 2,300,000
Data processing and communication charges	11,700,000	9,800,000	$ 9,500,000
Data Processing, Contract Termination and Conversion Cost Expenses	$ 1,300,000	$ 0	$ 800,000

Commitments and Contingencie116

Commitments and Contingencies - Future Estimated Payments Related to Data Processing and Communication Charges (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 11,360
2,017	11,743
2,018	12,123
2,019	12,527
2,020	12,951
Total	$ 60,704

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current									$ 24,825	$ 15,979	$ 16,836
Deferred									(427)	1,536	(2,358)
Total	$ 6,814	$ 6,407	$ 6,498	$ 4,680	$ 3,963	$ 4,906	$ 4,875	$ 3,771	$ 24,398	$ 17,515	$ 14,478

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Income Taxes [Line Items]
Gross Deferred Tax Assets	$ 48,729	$ 43,388
Net Deferred Tax Asset	34,749	$ 28,686
Change in deferred tax assets, net	$ 6,100
Statutory tax rate	35.00%	35.00%	35.00%
Valuation allowance related to gross deferred tax assets	$ 2,670	$ 2,249
Deferred tax assets operating loss carry forwards, total	26,700
Decrease to eliminate unrecognized tax benefit related to bad debts	0	$ 1,673	$ 0
Unrecognized tax benefits, accrued interest	$ 100		300
Unrecognized tax benefits, interest expense			$ 200
Minimum
Schedule Of Income Taxes [Line Items]
Deferred tax assets operating loss carry forwards, expiration date	2,020
Maximum
Schedule Of Income Taxes [Line Items]
Deferred tax assets operating loss carry forwards, expiration date	2,035
PENNSYLVANIA
Schedule Of Income Taxes [Line Items]
Valuation allowance related to gross deferred tax assets	$ 2,700
Integrity Bancshares, Inc.
Schedule Of Income Taxes [Line Items]
Gross Deferred Tax Assets	12,600
Net Deferred Tax Asset	$ 4,200

Income Taxes - Schedule of Stat

Income Taxes - Schedule of Statutory to Effective Tax Rate Reconciliation (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Statutory tax rate	35.00%	35.00%	35.00%
Low income housing tax credits	(4.40%)	(5.80%)	(6.80%)
Tax-exempt interest	(4.10%)	(4.60%)	(4.50%)
Bank owned life insurance	(0.80%)	(0.80%)	(1.00%)
Other	1.00%	(0.60%)	(0.40%)
Effective Tax Rate	26.70%	23.20%	22.30%

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of Temporary Differences with Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Liabilities:
Net unrealized holding gains on securities available-for-sale	$ (3,563)	$ (3,783)
Prepaid pension	(2,865)	(3,472)
Deferred loan income	(2,847)	(2,165)
Purchase accounting adjustments	0	(631)
Depreciation on premises and equipment	(1,226)	(1,590)
Other	(809)	(812)
Total Deferred Tax liabilities	(11,310)	(12,453)
Deferred Tax Assets:
Allowance for loan losses	17,740	17,567
Purchase accounting adjustments	1,298	0
Other employee benefits	2,556	2,453
Low income housing partnerships	4,531	4,049
Net adjustment to funded status of pension	12,425	11,089
Impairment of securities	1,354	1,313
State net operating loss carryforwards	2,670	2,249
Other	6,155	4,668
Gross Deferred Tax Assets	48,729	43,388
Less: Valuation allowance	(2,670)	(2,249)
Total Deferred Tax Assets	46,059	41,139
Net Deferred Tax Asset	$ 34,749	$ 28,686

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Change in Federal and State Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax related interest			$ 200
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 284	$ 1,902	978
Increase	818	55	924
Decrease	0	(1,673)	0
Current period tax positions	0	0	0
Reductions for statute of limitations expirations	0	0	0
Balance at End of Year	1,102	284	1,902
Amount That Would Affect the Effective Tax Rate if Recognized	$ 542	$ 184	$ 148

Tax Effects on Other Compreh122

Tax Effects on Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pre-Tax Amount
Net change in unrealized gains on securities available-for-sale	$ (663)	$ 11,825	$ (16,928)
Net available-for-sale securities losses reclassified into earnings	34	(41)	(5)
Adjustment to funded status of employee benefit plans	(3,551)	(13,394)	18,299
Other Comprehensive Income (Loss), Before Tax	(4,180)	(1,610)	1,366
Tax (Expense) Benefit
Net change in unrealized gains on securities available-for-sale, Tax (Expense) Benefit	232	(4,139)	5,925
Net available-for-sale securities gains reclassified into earnings, Tax (Expense) Benefit	(12)	15	2
Adjustment to funded status of employee benefit plans, Tax (Expense) Benefit	1,336	4,595	(6,405)
Income tax benefit (expense) related to items of other comprehensive income	1,556	471	(478)
Net of Tax Amount
Net change in unrealized gains on securities available-for-sale, Net of Tax Amount	(431)	7,686	(11,003)
Net available-for-sale securities gains reclassified into earnings, Net of Tax Amount	22	(26)	(3)
Adjustment to funded status of employee benefit plans, Net of Tax Amount	(2,215)	(8,799)	11,894
Other Comprehensive Income (Loss), After Tax	$ (2,624)	$ (1,139)	$ 888

Employee Benefits - Additional

Employee Benefits - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Number of consecutive years of employee's compensation	5 years
Number of total years of employee's compensation	10 years
Accumulated benefit obligation	$ 101,600,000	$ 104,300,000
Pension contributions	0
Projected benefit obligation	109,747,000	113,124,000	$ 95,969,000
Net periodic benefit cost	1,736,000	736,000	2,832,000
Level 1 to Level 2 transfers	0	0
Purchases, transfers or sales of level 3 plan assets	0
Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss included in accumulated other comprehensive income (loss)				$ (2,300,000)
Prior service credit expected recognized Amount				$ 100,000
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	4,000,000	3,500,000
Net periodic benefit cost	600,000	400,000	400,000
Defined benefit plan in accumulated other comprehensive gain/loss before tax	$ 2,100,000
Thrift Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions to the Thrift Plan	3.50%
Compensation expense	$ 1,500,000	$ 1,300,000	$ 1,400,000
Marketable equity securities
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation minimum	50.00%
Targeted asset allocation maximum	70.00%
Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation minimum	30.00%
Targeted asset allocation maximum	50.00%

Employee Benefits - Benefit Obl

Employee Benefits - Benefit Obligation and Plan Assets Deriving Funded Status, in Other Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plan, Actuarial Gain (Loss)	$ (4,257)	$ 16,020
Change in Projected Benefit Obligation
Projected benefit obligation at beginning of year	113,124	95,969
Service cost	2,601	2,369	$ 2,767
Interest cost	4,425	4,470	3,985
Benefits paid	(6,146)	(5,704)
Projected Benefit Obligation at End of Year	109,747	113,124	95,969
Change in Plan Assets
Fair value of plan assets at beginning of year	93,486	89,556
Actual return on plan assets	(2,755)	9,634
Benefits paid	(6,146)	(5,704)
Fair Value of Plan Assets at End of Year	84,585	93,486	$ 89,556
Funded Status	$ (25,162)	$ (19,638)

Employee Benefits - Accumulated

Employee Benefits - Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Prior service credit	$ (1,029)	$ (1,167)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Actuarial Gain (Loss), before Tax	34,376	30,726
Net actuarial loss	$ (33,347)	$ (29,559)

Employee Benefits - Actuarial W

Employee Benefits - Actuarial Weighted Average Assumptions Used in Determining Benefit Obligation (Detail)	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Discount rate	4.25%	4.00%
Rate of compensation increase	3.00%	3.00%

Employee Benefits - Components

Employee Benefits - Components of Net Periodic Pension Cost and Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of Net Periodic Pension Cost
Service cost-benefits earned during the period	$ 2,601	$ 2,369	$ 2,767
Interest cost on projected benefit obligation	4,425	4,470	3,985
Expected return on plan assets	(7,180)	(6,907)	(6,207)
Amortization of prior service cost (credit)	(138)	(137)	(138)
Recognized net actuarial loss	2,028	941	2,425
Net Periodic Pension Expense	1,736	736	2,832
Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Income (Loss)
Net actuarial loss (gain)	5,678	13,294	(15,499)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Actuarial Gain (Loss), before Tax	2,028	941	2,425
Recognized prior service credit	138	137	138
Total (Before Tax Effects)	3,788	12,490	(17,786)
Total Recognized in Net Benefit Cost and Other Comprehensive Income (Loss) (Before Tax Effects)	$ 5,524	$ 13,226	$ (14,954)

Employee Benefits - Actuaria128

Employee Benefits - Actuarial Weighted Average Assumptions Used in Determining Net Periodic Pension Cost (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Discount rate	4.00%	4.75%	4.00%
Rate of compensation increase	3.00%	3.00%	3.00%
Expected return on assets	8.00%	8.00%	8.00%

Employee Benefits - Estimated F

Employee Benefits - Estimated Future Benefit Payments (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Compensation and Retirement Disclosure [Abstract]
2,016	$ 6,455
2,017	6,250
2,018	6,643
2,019	6,676
2,020	7,298
2021-2025	$ 38,488

Employee Benefits - Pension Pla

Employee Benefits - Pension Plan Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 84,585	$ 93,486
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,371	5,073
Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	27,054	26,726
Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,421	3,728
Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	50,739	57,085
International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		874
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	81,214	88,413
Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 1 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	27,054	26,726
Level 1 | Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,421	3,728
Level 1 | Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	50,739	57,085
Level 1 | International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		874
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,371	5,073
Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,371	5,073
Level 2 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 | Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 | Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 | International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 0	0
Level 3 | International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		$ 0

Incentive and Restricted Sto131

Incentive and Restricted Stock Plan and Dividend Reinvestment Plan - Additional Information (Detail) - USD ($)	12 Months Ended			120 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards outstanding (in shares)	0	155,500	428,900	0	675,500
Nonstatutory stock options granted since 2006	0	0	0
Aggregate intrinsic value of options outstanding		$ 0	$ 0
Aggregate intrinsic value of options exercisable		0	$ 0
Restricted shares granted			3,247
Compensation expense	$ 1,700,000	900,000	$ 600,000
Tax benefit realized on compensation expense	600,000	$ 300,000	$ 200,000
Unrecognized compensation expense to be recognized	$ 2,300,000			$ 2,300,000
Weighted average compensation expense recognize period	1 year 7 months 28 days
Outside Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Restricted shares granted	16,142	13,824	18,942
Senior Management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	71,699	66,631
Time-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Award vesting after year two, percent			50.00%
Restricted Stock Award vesting after year three, percent			50.00%
2003 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of common stock authorized (in shares)	1,500,000			1,500,000
Stock plan expiration period	10 years
Number of awards to be granted (in shares)	0			0
Number of awards outstanding (in shares)	0			0
Vesting period	10 years
Nonstatutory stock options granted since 2006				0
Restricted shares granted	259,673
2003 Stock Plan | Senior Management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted			3,247
2014 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of common stock authorized (in shares)	750,000			750,000
Stock plan expiration period	10 years
Restricted shares granted	168,296
2014 LTIP | Senior Management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	71,699	66,631

Incentive and Restricted Sto132

Incentive and Restricted Stock Plan and Dividend Reinvestment Plan - Summary of Nonstatutory Stock Options Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Nonstatutory Stock Option Activity (shares) [Roll Forward]
Outstanding, beginning of year (in shares)	155,500	428,900	675,500
Granted (in shares)	0	0	0
Exercised (in shares)	0	0	0
Forfeited (in shares)	0	(273,400)	(246,600)
Expired (in shares)	(155,500)	0	0
Outstanding, End of year (in shares)	0	155,500	428,900
Exercisable at End of Year (in shares)	0	155,500	428,900
Nonstatutory Stock Options, Outstanding, Weighted Average Exercise Price (dollars per share) [Abstract]
Outstanding at beginning of year (in dollars per share)	$ 37.86	$ 37.36	$ 35.18
Granted (in dollars per share)	0	0	0
Exercised (in dollars per share)	0	0	0
Forfeited (in dollars per share)	0	37.08	31.39
Expired (in dollars per share)	37.86	0	0
Outstanding and End of Year (in dollars per share)	0	37.86	37.36
Exercisable at End of Year (in dollars per share)	$ 0	$ 37.86	$ 37.36
Outstanding at End of Year (in years)	0 years	1 year	1 year 4 months 24 days
Exercisable at End of Year (in years)	0 years	1 year	1 year 4 months 24 days

Incentive and Restricted Sto133

Incentive and Restricted Stock Plan and Dividend Reinvestment Plan - Summary of Non-Vested Restricted Stock (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Nonvested, Number of Shares (shares) [Roll Forward]
Granted, Restricted Stock (in shares)			3,247
2003 Stock Plan
Nonvested, Number of Shares (shares) [Roll Forward]
Granted, Restricted Stock (in shares)	259,673
2003 Stock Plan | Restricted Stock
Nonvested, Number of Shares (shares) [Roll Forward]
Beginning of period (in shares)	23,145	79,415
Granted, Restricted Stock (in shares)	0	0
Vested, Restricted Stock (in shares)	15,433	41,740
Forfeited, Restricted Stock (in shares)	7,712	14,530
End of period (in shares)	0	23,145	79,415
Nonvested shares, Weighted Average Grant Date Fair Value (dollars per share) [Abstract]
Beginning of period (in dollars per share)	$ 23.28	$ 21.50
Granted (in dollar per share)	0	0
Vested (in dollar per share)	22.34	20.70
Forfeited (in dollar per share)	22.34	20.97
End of period (in dollars per share)	$ 0	$ 23.28	$ 21.50
2014 Stock Plan
Nonvested, Number of Shares (shares) [Roll Forward]
Granted, Restricted Stock (in shares)	168,296
2014 Stock Plan | Restricted Stock
Nonvested, Number of Shares (shares) [Roll Forward]
Beginning of period (in shares)	79,824	0
Granted, Restricted Stock (in shares)	87,841		80,455
Vested, Restricted Stock (in shares)	14,126		158
Forfeited, Restricted Stock (in shares)	3,183		473
End of period (in shares)	150,356	79,824	0
Nonvested shares, Weighted Average Grant Date Fair Value (dollars per share) [Abstract]
Beginning of period (in dollars per share)	$ 23.24	$ 0
Granted (in dollar per share)	28.71		$ 23.24
Vested (in dollar per share)	23.57		23.19
Forfeited (in dollar per share)	26.15		23.19
End of period (in dollars per share)	$ 26.34	$ 23.24	$ 0

Parent Company Condensed Fin134

Parent Company Condensed Financial Information - Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Information [Line Items]
Cash	$ 99,399	$ 109,580	$ 108,356	$ 337,711
Other assets	102,583	97,024
Total Assets	6,318,354	4,964,686
Other liabilities	68,758	61,789
Total Liabilities	5,526,117	4,356,297
Total Shareholders' Equity	792,237	608,389	571,306	537,422
Total Liabilities and Shareholders’ Equity	6,318,354	4,964,686
Parent Company
Condensed Financial Information [Line Items]
Cash	12,595	38,028	$ 14,852	$ 12,202
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	777,795	565,927
Nonbank subsidiaries	20,624	20,569
Other assets	2,530	5,567
Total Assets	813,544	630,091
Long-term debt	20,619	20,619
Other liabilities	688	1,083
Total Liabilities	21,307	21,702
Total Shareholders' Equity	792,237	608,389
Total Liabilities and Shareholders’ Equity	$ 813,544	$ 630,091

Parent Company Condensed Fin135

Parent Company Condensed Financial Information - Statements of Net Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Information [Line Items]
Interest expense on long-term debt	$ 790	$ 617	$ 746
Net Income	67,081	57,910	50,539
Parent Company
Condensed Financial Information [Line Items]
Dividends from subsidiaries	75,413	46,414	24,087
Investment income	19	19	15
Interest expense on long-term debt	773	759	769
Other expenses	2,138	2,014	2,579
Income before Equity in Undistributed Net Income of Subsidiaries	72,521	43,660	20,754
Bank subsidiary	(5,064)	13,351	29,926
Nonbank subsidiaries	(376)	899	(141)
Net Income	$ 67,081	$ 57,910	$ 50,539

Parent Company Condensed Fin136

Parent Company Condensed Financial Information - Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Information [Line Items]
Net Income	$ 67,081	$ 57,910	$ 50,539
Tax benefit from stock-based compensation	(53)	(16)	(96)
Net Cash Provided by Operating Activities	60,584	78,103	86,076
Net Cash Used in Investing Activities	(405,737)	(437,048)	(309,683)
Cash dividends paid to common shareholders	(24,487)	(20,203)	(18,137)
Tax benefit from stock-based compensation	53	16	96
Net Cash Provided by (Used in) Financing Activities	334,972	360,169	(5,748)
Net increase (decrease) in cash	(10,181)	1,224	(229,355)
Cash and cash equivalents at beginning of year	109,580	108,356	337,711
Cash and Cash Equivalents at End of Year	99,399	109,580	108,356
Parent Company
Condensed Financial Information [Line Items]
Net Income	67,081	57,910	50,539
Equity in undistributed (earnings) losses of subsidiaries	5,440	(14,250)	(29,785)
Tax benefit from stock-based compensation	(53)	(16)	(96)
Other	3,059	(106)	121
Net Cash Provided by Operating Activities	75,527	43,538	20,779
Net investments in subsidiaries	(38,404)	0	0
Acquisitions	(29,510)	0	0
Net Cash Used in Investing Activities	(67,914)	0	0
Repayment of junior subordinated debt	(8,500)	0	0
(Purchase) Sale of treasury shares, net	(112)	(163)	(88)
Cash dividends paid to common shareholders	(24,487)	(20,215)	(18,137)
Tax benefit from stock-based compensation	53	16	96
Net Cash Provided by (Used in) Financing Activities	(33,046)	(20,362)	(18,129)
Net increase (decrease) in cash	(25,433)	23,176	2,650
Cash and cash equivalents at beginning of year	38,028	14,852	12,202
Cash and Cash Equivalents at End of Year	$ 12,595	$ 38,028	$ 14,852

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Banking and Thrift [Abstract]
Total trust preferred securities	$ 20
Junior subordinated debt, included in Tier 2 capital	$ 25

Regulatory Matters - Summary of

Regulatory Matters - Summary of Risk-Based Capital Amounts and Ratios for S&T and S&T Bank (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
S&T
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Leverage Ratio, Actual Amount	$ 535,234	$ 465,114
Leverage Ratio, Actual Ratio	8.96%	9.80%
Leverage Ratio, Minimum Regulatory Capital Requirements Amount	$ 238,841	$ 189,895
Leverage Ratio, Minimum Regulatory Capital Requirements Ratio	4.00%	4.00%
Leverage Ratio, To be Well Capitalized Amount	$ 298,551	$ 237,369
Leverage Ratio, To be Well Capitalized Ratio	5.00%	5.00%
Tier One Common Equity Capital	$ 515,234	$ 445,114
Tier One Common Equity Capital to Risk Weighted Assets	9.77%	11.81%
Tier One Common Equity Capital Required for Capital Adequacy	$ 237,315	$ 169,621
Tier One Common Equity Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier One Common Equity Capital Required to be Well Capitalized	$ 342,788	$ 245,008
Tier One Common Equity Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	$ 535,234	$ 465,114
Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio	10.15%	12.34%
Tier 1 Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Amount	$ 316,419	$ 150,774
Tier 1 Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Ratio	6.00%	4.00%
Tier 1 Capital (to Risk-Weighted Assets), To be Well Capitalized Amount	$ 421,892	$ 226,161
Tier 1 Capital (to Risk-Weighted Assets), To be Well Capitalized Ratio	8.00%	6.00%
Total Capital (to Risk-Weighted Assets), Actual Amount	$ 611,859	$ 537,935
Total Capital (to Risk-Weighted Assets), Actual Ratio	11.60%	14.27%
Total Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Amount	$ 421,892	$ 301,548
Total Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Ratio	8.00%	8.00%
Total Capital (to Risk-Weighted Assets), To be Well Capitalized Amount	$ 527,366	$ 376,936
Total Capital (to Risk-Weighted Assets), To be Well Capitalized Ratio	10.00%	10.00%
S&T Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Leverage Ratio, Actual Amount	$ 502,114	$ 403,593
Leverage Ratio, Actual Ratio	8.43%	8.53%
Leverage Ratio, Minimum Regulatory Capital Requirements Amount	$ 238,121	$ 189,182
Leverage Ratio, Minimum Regulatory Capital Requirements Ratio	4.00%	4.00%
Leverage Ratio, To be Well Capitalized Amount	$ 297,651	$ 236,477
Leverage Ratio, To be Well Capitalized Ratio	5.00%	5.00%
Tier One Common Equity Capital	$ 502,114	$ 403,593
Tier One Common Equity Capital to Risk Weighted Assets	9.55%	10.76%
Tier One Common Equity Capital Required for Capital Adequacy	$ 236,482	$ 168,804
Tier One Common Equity Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier One Common Equity Capital Required to be Well Capitalized	$ 341,584	$ 243,827
Tier One Common Equity Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier 1 Capital (to Risk-Weighted Assets), Actual Amount	$ 502,114	$ 403,593
Tier 1 Capital (to Risk-Weighted Assets), Actual Ratio	9.55%	10.76%
Tier 1 Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Amount	$ 315,309	$ 150,048
Tier 1 Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Ratio	6.00%	4.00%
Tier 1 Capital (to Risk-Weighted Assets), To be Well Capitalized Amount	$ 420,412	$ 225,071
Tier 1 Capital (to Risk-Weighted Assets), To be Well Capitalized Ratio	8.00%	6.00%
Total Capital (to Risk-Weighted Assets), Actual Amount	$ 577,824	$ 475,538
Total Capital (to Risk-Weighted Assets), Actual Ratio	11.00%	12.68%
Total Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Amount	$ 420,412	$ 300,095
Total Capital (to Risk-Weighted Assets), Minimum Regulatory Capital Requirements Ratio	8.00%	8.00%
Total Capital (to Risk-Weighted Assets), To be Well Capitalized Amount	$ 525,515	$ 375,119
Total Capital (to Risk-Weighted Assets), To be Well Capitalized Ratio	10.00%	10.00%

Segments - Additional Informati

Segments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015segment
Segment Reporting [Abstract]
Number of reportable segments	3

Segments - Total Assets by Repo

Segments - Total Assets by Reportable Operating Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets	$ 6,318,354	$ 4,964,686
Community Banking
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets	6,305,046	4,954,728
Insurance
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets	9,619	7,468
Wealth Management
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets	$ 3,689	$ 2,490

Segments - Financial Informatio

Segments - Financial Information of Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	$ 53,353	$ 53,669	$ 52,611	$ 43,916	$ 41,381	$ 40,605	$ 39,872	$ 38,665	$ 203,548	$ 160,523	$ 153,756
Interest expense	4,468	4,073	3,800	3,657	3,315	3,076	3,017	3,074	15,997	12,481	14,563
NET INTEREST INCOME									187,551	148,042	139,193
Provision for loan losses	3,915	3,206	2,059	1,207	1,106	1,454	(1,134)	289	10,388	1,715	8,311
Noninterest income	13,084	12,481	13,417	12,084	11,220	11,931	11,731	11,415	51,033	46,338	51,527
Noninterest Expense	33,817	33,829	35,449	33,621	29,720	28,440	30,165	28,914	136,717	117,240	117,392
Noninterest expense									130,160	112,646	112,294
Depreciation expense									4,739	3,465	3,507
Amortization of intangible assets									1,818	1,129	1,591
Provision (benefit) for income taxes	$ 6,814	$ 6,407	$ 6,498	$ 4,680	$ 3,963	$ 4,906	$ 4,875	$ 3,771	24,398	17,515	14,478
Net Income									67,081	57,910	50,539
Operating Segments | Community Banking
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income									203,439	160,403	153,450
Interest expense									16,678	13,989	16,508
NET INTEREST INCOME									186,761	146,414	136,942
Provision for loan losses									10,388	1,715	8,311
Noninterest income									34,106	29,443	34,649
Noninterest expense									115,998	97,733	94,769
Depreciation expense									4,664	3,387	3,430
Amortization of intangible assets									1,738	1,039	1,492
Provision (benefit) for income taxes									23,209	16,311	14,180
Net Income									64,870	55,672	49,409
Operating Segments | Insurance
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income									2	2	2
Interest expense									0	0	0
NET INTEREST INCOME									2	2	2
Provision for loan losses									0	0	0
Noninterest income									5,035	5,279	5,483
Noninterest expense									4,365	4,313	5,210
Depreciation expense									50	51	47
Amortization of intangible assets									50	51	51
Provision (benefit) for income taxes									200	303	(47)
Net Income									372	563	224
Operating Segments | Wealth Management
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income									508	518	517
Interest expense									0	0	0
NET INTEREST INCOME									508	518	517
Provision for loan losses									0	0	0
Noninterest income									11,412	11,297	10,662
Noninterest expense									9,037	9,173	9,850
Depreciation expense									25	27	30
Amortization of intangible assets									30	39	48
Provision (benefit) for income taxes									989	901	345
Net Income									1,839	1,675	906
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income									(401)	(400)	(213)
Interest expense									(681)	(1,508)	(1,945)
NET INTEREST INCOME									280	1,108	1,732
Provision for loan losses									0	0	0
Noninterest income									480	319	733
Noninterest expense									760	1,427	2,465
Depreciation expense									0	0	0
Amortization of intangible assets									0	0	0
Provision (benefit) for income taxes									0	0	0
Net Income									$ 0	$ 0	$ 0

Selected Financial Data - Summa

Selected Financial Data - Summary of Selected Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 53,353	$ 53,669	$ 52,611	$ 43,916	$ 41,381	$ 40,605	$ 39,872	$ 38,665	$ 203,548	$ 160,523	$ 153,756
Interest expense	4,468	4,073	3,800	3,657	3,315	3,076	3,017	3,074	15,997	12,481	14,563
Provision for loan losses	3,915	3,206	2,059	1,207	1,106	1,454	(1,134)	289	10,388	1,715	8,311
Net Interest Income After Provision for Loan Losses	44,970	46,390	46,752	39,052	36,960	36,075	37,989	35,302	177,163	146,327	130,882
Security gains, net	0	0	(34)	0	0	0	40	1
Noninterest income	13,084	12,481	13,417	12,084	11,220	11,931	11,731	11,415	51,033	46,338	51,527
Noninterest expense	33,817	33,829	35,449	33,621	29,720	28,440	30,165	28,914	136,717	117,240	117,392
Income before taxes	24,237	25,042	24,686	17,515	18,460	19,566	19,595	17,804
Provision for income taxes	6,814	6,407	6,498	4,680	3,963	4,906	4,875	3,771	24,398	17,515	14,478
Net Income Available to Common Shareholders	$ 17,423	$ 18,635	$ 18,188	$ 12,835	$ 14,497	$ 14,660	$ 14,720	$ 14,033	$ 66,801	$ 57,745	$ 50,392
Common earnings per share-diluted (in USD per share)	$ 0.50	$ 0.54	$ 0.52	$ 0.41	$ 0.49	$ 0.49	$ 0.49	$ 0.47	$ 1.98	$ 1.95	$ 1.70
Dividends declared per common share (in USD per share)	0.19	0.18	0.18	0.18	0.18	0.17	0.17	0.16	$ 0.73	$ 0.68	$ 0.61
Common book value (in USD per share)	$ 22.76	$ 22.63	$ 22.15	$ 21.91	$ 20.42	$ 20.33	$ 20.04	$ 19.64

Sale of Merchant Card Servic143

Sale of Merchant Card Servicing Business - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business		$ 0	$ 0	$ 4,750
Gain on sale of business		$ 0	$ 0	$ 3,093
Merchant Card Servicing Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business	$ 4,800
Termination fee	1,700
Gain on sale of business	$ 3,100
Initial term of agreement		10 years